New York, New York - Claudio Neves Valente came to the US as an ambitious physics student at Brown University, but ended his life while hiding from police after allegedly killing two students at the Ivy League institution, as well as an MIT professor.

Authorities say Valente – a 48-year-old Portuguese national – shot dead Brown students Ella Cook and Mukhammad Aziz Umurzokov, and wounded several others, on December 13 before heading to the home of renowned Massachusetts Institute of Technology professor Nuno Loureiro and killing him two days later.

The Chief Medical Examiner's office released autopsy results Friday, saying Neves Valente "died as a result of a gunshot wound to the head, and that his manner of death was a suicide."

He is "estimated to have died December 16," the medical examiner said.

Murder Brown University mass shooter still on the run as police seek individual who may have "information"

Federal officials also released results of early ballistic and DNA testing on Friday.

"Two 9mm pistols were recovered in New Hampshire with the body," according to a joint statement from the FBI and federal Alcohol, Tobacco and Firearm (ATF) agency officials.

One of the two firearms recovered "is positively correlated with the firearm used in the Brown University mass shooting. The other of the two firearms is positively correlated with the murder of" Loureiro, the statement said.

The FBI-ATF statement also said a rapid DNA test "has preliminarily matched Neves Valente with DNA recovered from evidence at Brown University," without mentioning any testing at the MIT professor's home.

The FBI-ATF statement did not say whether either of the recovered guns was used in the shooter's suicide, one of many questions that still loom about the incidents.

No motive has been made public for any of the killings, which cast a long shadow on two of New England's normally genteel elite universities. It has been suggested that he did not know the students.

Portuguese media outlet Expresso reported that Valente, from Torres Novas in central Portugal, attended Lisbon's IST institution at the same time as Loureiro.

They were classmates, and Valente was the top student that year.

"Most classmates have no memory of the student Claudio Valente, other than the fact that he was the best in the class that year," IST president Rogerio Colaco told the outlet.

Murder Rob and Michele Reiner's kids break silence as their brother faces murder charges

By contrast, Loureiro – who taught nuclear science and engineering as well as physics – maintained links with IST professors, he added.

Investigators struggled to produce viable leads in the days after the incidents, with President Donald Trump criticizing Brown University for failing to link its security cameras to police systems.

During the protracted manhunt, dozens of names surfaced on social media and elsewhere in connection with the shooting -- almost all false and unlinked to the bloodshed.

Rhode Island officials denounced the misinformation, saying it complicated their investigation.

As the media reported the name of a military veteran initially detained and released, social media filled with his image – and a torrent of erroneous posts sharing photos of another man with the same name.

Colonel Darnell Weaver, superintendent of the Rhode Island State Police, said "the endless barrage of misinformation, disinformation, rumors, leaks and clickbait were not helpful in this investigation."

But it was a tip from an often murky, irreverent corner of the internet – Reddit – that was the breakthrough for detectives.

Officers were directed to a post on the social media forum site that told investigators to probe a grey Nissan SUV.

A tipster called "John" by investigators then came forward and described to officers an encounter with a suspicious man at Brown prior to the slayings.

The information was crucial for the investigation and allowed officers to link the Brown campus shootings and the MIT professor's murder.

In their briefing announcing the conclusion of the case, officials revealed that Valente had taken elaborate steps to conceal his identity, including using false license plates and a cell phone that investigators struggled to trace.

The hunt for the Brown gunman dragged into a sixth day until officers found Valente's body in a self-storage facility in Salem, Massachusetts.

Questions continued to swirl around the episode.

Rhode Island Attorney General Peter Neronha told the Thursday briefing "in terms of why Brown? I think that's a mystery."