The suspect in last week's mass shooting at Brown University has been found dead in a storage facility in Salem, New Hampshire, following a six-day multi-state manhunt, police say.

They identified the suspect as Claudio Neves Valente, 48, a Portuguese national who studied at the university in Providence, Rhode Island, about 25 years ago.

Providence police chief Oscar Perez said video evidence and tips from the public led investigators to a car-rental location where they found the suspect's name and matched him to their person of interest.

Officials said they also believe Valente killed a Massachusetts Institute of Technology (MIT) professor two days after the December 13 shooting at Brown.

Initial findings suggest Valente died of a self-inflicted gunshot wound, and police were unable to comment on how long he might have been inside the storage facility.

Authorities have not suggested a motive for either attack.

Brown University president Christina Paxson said that Valente was enrolled at the Ivy League school from autumn of 2000 to the following spring, and was studying for a PhD in physics. He had no current active affiliation to Brown, she said.

Officials said they believe Valente shot and killed MIT professor Nuno F Gomes Loureiro, 47, on Monday at his home in Brookline, which is about 50 miles (80km) from Providence.

Both the victim and the suspect had studied at the same university in Portugal in the late 1990s, police said.

The cases were linked when the suspect's vehicle was identified via CCTV footage and a witness at Brown University.

Rhode Island Attorney General Peter Neronha said Valente was found dead with a satchel and two firearms. Evidence in a car nearby matched to the scene in Providence.

The same car was spotted near the scene of the professor's shooting.

Even though the suspect was found dead, FBI Special Agent-in-Charge Ted Docks stated, our work is not done. There are many questions that need to be answered, highlighting that approximately 500 agents were deployed to assist local authorities.

Meanwhile, the US has suspended its green card lottery scheme in the wake of the shooting, with Homeland Security Secretary Kristi Noem saying Valente should never have been allowed in our country. Noem noted that Valente had entered the US through the diversity lottery immigrant visa programme (DV1) in 2017.

This tragic event has raised numerous issues surrounding gun violence and immigration policies in the United States.