Updated at 8:20 p.m. ET: MEXICO CITY -- Mexican troops have arrested two suspects in the killing of a U.S. Border Patrol agent and the wounding of a second officer in Arizona, Mexican security officials said on Wednesday. 

The two suspects were detained in a Mexican military operation in the city of Agua Prieta, in Mexico's northern Sonora state, a few miles from the spot where Nicholas Ivie was shot dead early on Tuesday while responding to a tripped ground sensor, a Mexican Army officer, who declined to be named, told Reuters.

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Ivie was among three agents who were patrolling on foot about five miles north of the international border when gunfire erupted. A second agent was also wounded while the third, a woman, was unharmed.  

The agents had been patrolling in an area near the border town of Naco, well-known as a corridor for smuggling, and the Cochise County Sheriff's department has said that tracks were found heading south after the shooting.

Related: Feds examine whether friendly fire killed border agent

Ivie was a 30-year-old father of two who grew up in Utah and was active in the Mormon Church. He had been an agent for four years.

A Mexican police official in Naco, across the border from the Arizona town of the same name, confirmed the arrests, which occurred in the early hours of Wednesday.

U.S. officials refused to comment on the report of the arrests to NBC News.

It was the first fatal shooting of an on-duty Border Patrol agent since December 2010, when Brian Terry was killed in a shootout with bandits near the border. Terry's shooting was later linked to the government's "Fast and Furious" gun-smuggling operation, which allowed people suspected of illegally buying guns for others to walk away from gun shops with weapons, rather than be arrested.

Two Border Patrol agents were killed last year in an accident during a car chase with smugglers near Phoenix.

Reuters and The Associated Press contributed to this report.

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A 7-year-old British girl whose parents and grandmother were murdered in a shooting spree during a family vacation in the French Alps last week spoke to investigators on Monday.

Zainab al-Hilli was shot and severely beaten during the attack and placed in a medically-induced coma.

Zainab, who awoke from the coma on Sunday, was visited by French police in what was characterized as an introduction and a chance for the girl to grow accustomed to investigators, and so that they may gradually earn her trust.

7-year-old girl in French Alps shooting awakes from coma

“They have been able to speak to her but this was just an initial meeting,” a source close to the investigation told ITV News. “They could not go into any detail and the child was very tired. It was not permitted for the discussion to go any further.”

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Zeena, Zainab’s 4-year-old sister, also survived the shootings and returned to Britain on Sunday. She was found eight hours after authorities arrived on the crime scene, hiding beneath her deceased mother's skirt in the car.

Read more about the French Alps killings on ITV News

It was unclear if the girls have been told that their British-Iraqi father Saad al-Hilli, mother Iqbal and grandmother were killed in the attack.

Hilli, a mechanical engineer who worked with Surrey Satellite Technology, a subsidiary of the aerospace and defense firm EADS, and the other victims were shot in what appeared to be execution-style killings.

Family feud behind massacre in French Alps?

Also killed was French cyclist Sylvain Mollier, a 45-year-old father of three who authorities suspect was in the wrong place at the wrong time when he came upon the murder.

At the al-Hilli’s $1.6 million home in Surrey, a suburb southwest of London, police searched for clues to solve the mysterious slayings and at one point called in a bomb squad disposal vehicle as a precaution.

A safe inside the al-Hilli residence was being forcibly opened with power tools on Monday, ITV News reported.

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Investigators at scene have revealed that four of the shooting victims were each shot twice in the head with the same gun, a 7.65 self-loading automatic pistol with 10 bullets in it. However, since about 25 shells were recovered from the scene and the bodies of the victims it was suggested that whoever did the killing must have reloaded at least twice, ITV News reported.

Still, five days since a British cyclist came across the chilling murder scene, a motive and suspect continue to elude police.

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Investigators have said they were looking at various theories, including robbery, a family feud, a possible link to Hilli's work in the aerospace industry or his Iraqi origins.

ITV News is the UK partner of NBC News.

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Updated at 10:48 p.m. ET: A cyclist came across a chilling scene Wednesday afternoon as he climbed a wooded road in southeastern France at the foothills of the French Alps: Three dead bodies in a BMW registered in Britain.

Nearby was the body of another cyclist, dressed in cycling gear, his bike nearby.

A slain man was seated at the BMW's steering wheel; the two dead women were in the back seats. The sole survivor was a girl – news reports dispute whether she is 8- or 10-years-old – who had been shot three times, according to Le Dauphiné Libéré. The cyclist found her in front of the car.

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The passing cyclist called "les secours" – France’s 911 – and the girl was transported by plane to Grenoble, where she was being treated. Police have secured her hospital room, officials said. Authorities believe the attack may have been the result of an attempted robbery or hijacking, the Independent reported.

 

The BMW was parked in a lot between two small villages – Chevaline and Doussard – at the upper part of Lake Annecy in the Haute Savoie region in southeastern France, news reports said. Although the region is a British tourist destination known for its hiking trails and wooded beauty, the summer crowds have dwindled.

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Police believe the victims were shot between 3 p.m. and 4 p.m. – just 10 minutes before the cyclist came upon the car. Sixty casings littered the crime scene, but a gun was not found, they said, which could rule out domestic violence as the reason for the deaths.

French authorities have contacted British officials but said they did not know the identities or nationalities of the victims.

"For right now, we cannot form a single theory," said Eric Maillaud, a public prosecutor for the Annecy region, according to Le Dauphiné. He said the discovery looked like a scene from a movie, the Scotsman reported.

The cyclist who found the bodies and the girl was in shock as he was interviewed by police, according to news reports.

The bodies will remain at the crime scene overnight, the Independent reported; autopsies will be performed in a day or two.

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French authorities said on Friday they feared a serial killer was on the loose after a gunman shot dead a 47-year-old mother near her home in a Paris suburb, using a weapon employed in three other killings in the same area within the last five months.

"This series of killings deserves our maximum attention and we are putting all our resources into this affair," Interior Minister Claude Gueant told Europe 1 radio.

In each of the four shootings, the first of which was in November, a lone gunman used the same 7.65 mm caliber semi-automatic pistol, prosecutors said. The latest shooting took place on Thursday when a gunman on a motorbike struck.

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"It was a pistol, a semi-automatic pistol," said Marie-Suzanne Le Queau, public prosecutor in Evry, a commune in the southern suburbs of Paris. "This element alone is not enough to affirm at this stage that it is all part of the same affair."

There were obvious similarities in the way the latest three killings were carried out in February, March and April, but no clear link to the first killing in November, she added.

Around 100 investigators were working on the case and police were examining several leads, she said. The woman was a widow and had an 18-year-old son, Le Monde reported.

The motives of the murders remain a mystery, Le Monde wrote, as the last two victims appear to have no connection with the first two and come from very different backgrounds.

Reuters contributed to this report.

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Al-Qaida’s Internet message forums, which it uses to communicate its messages to the world, have been crippled in a suspected organized cyber-attack, according to a terrorism expert.

Three of the terror network’s main forums – Al-Shamukh, Al-Fidaa, and Ansar al-Mujahideen – have gone offline, said Evan Kohlmann, a terrorism analyst for NBC News. The most important, Al-Shamukh, has been inaccessible for almost five days, he told msnbc.com in an email.

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“An event of this scale very rarely occurs -- less than five times in the last five years -- and is usually the result of deliberate actions taken by a major international government,” Kohlmann said.

“The last time there was an outage of this duration, it was later revealed to be the work of British government hackers intent on delaying the distribution of the English-language Inspire Magazine produced by Al-Qaida in the Arabian Peninsula in June 2010,” he added.

Hacker attack cripples al-Qaida web communications

Kohlmann speculated that the outage could be an attempt to prevent the circulation of a footage taken by Mohamed Merah, the Islamist extremist who recorded his gun attacks in France that killed seven people, including three children shot dead at close range.

Before Merah was killed in a gunfight with police at his Toulouse apartment on Thursday, he told investigators he had posted his footage on the web. However, the video has not yet surfaced.

"It is impossible to say for certain, but these sorts of outages seem to be most often tied to the release of high-profile terrorist media," Kohlmann said. "There is nothing more hotly-anticipated right now among hardcore jihadists than a video recording of the reprehensible acts allegedly carried out in France."

The Department of Defense did not immediately comment on the outages.

Defense officials have told NBC News that the Army staff sergeant who allegedly shot and killed 16 Afghan civilians, including nine children, admitted his actions to fellow soldiers just before he was taken into custody.

"I did it," he is said to have told them.

According to the officials, a search party that included helicopters was formed after an Afghan soldier reported the American had left their small remote outpost in the early morning hours. In the meantime, the base received word that a number of civilians had been killed in a shooting spree at a nearby village.

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Overhead surveillance first spotted the soldier on his stomach in a field, either attempting to hide or crawl toward the base.  He eventually stood up and walked a short distance to the base where he was confronted and asked about the shootings at the village.  The officials say the staff sergeant replied "I did it."  At that point he was disarmed and taken into custody.  He then asked for a lawyer and has refused to talk ever since.

 

The officials also said they’ve received reports that the soldier was having marital problems and had recently received a troubling letter or email from his wife. According to one official, after four combat deployments it’s not unusual there would be stress on the family.

Defense officials also told NBC News that investigators have reason to believe that alcohol "may" have been a contributing factor in the shooting spree.

The investigation found bottles of alcohol on the small remote base where the staff sergeant was deployed.  The officials emphasize "may" because they say that nowhere in the reporting from the field is there any indication the staff sergeant was inebriated.

The soldier, reportedly married with two children, enlisted in the Army soon after the terror attacks of Sept. 11 and did three combat tours in Iraq before arriving in Kandahar, near where the shootings took place, in December 2011.

US soldier accused in Afghan massacre had brain injury history

Reports that the soldier had received post-traumatic stress disorder examinations are not unusual, since every soldier coming out of combat is routinely screened for PTSD.

The soldier suffered some minor traumatic brain injury in a rollover in Iraq in 2010, but that part of his medical history does not appear at this point to be a factor, according to the officials. They also said the man has a clean medical and behavior record.

Obama: Killing Afghans as serious as killing Americans

Col. Gary Kolb, a spokesman for the U.S.-led military coalition in Kabul, told The Associated Press a 48-hour probable cause assessment has been completed and that the service member continues to be confined.

Additionally, the officials told NBC News that the the military is considering capital murder charges against the soldier, meaning he could face the death penalty if convicted. They said the military also intends to conduct his court martial hearing in Afghanistan. Not only would it send the right signal to the Afghan people, officials said, but trying him in the United States or another country in the region would also present a logistics nightmare given the number of witnesses that would be expected to testify.

Military investigators in Afghanistan hope to file charges and release the identity of the soldier by the end of the week, but warn it could take another two weeks.

The Associated Press contributed to this report.

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