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 13 December 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, and the investigation continues with numerous questions still to answer.

Brown University president Christina Paxson confirmed Valente's past attendance at the school and noted he had no current active affiliation to it. Both the suspect and the MIT victim, professor Nuno F Gomes Loureiro, had studied at the same university in Portugal in the late 1990s.

Echoing the concerns regarding safety, US authorities have suspended the green card lottery program which Valente utilized to enter the country, as part of a broader policy response in the wake of this tragedy.