The suspect in the mass shooting at Brown University is dead, as investigators say he also killed a Massachusetts Institute of Technology professor two days after the rampage at Brown.
Officials said the gunman, identified as Portuguese national Claudio Neves Valente, attended Brown University more than two decades ago but his motive remains a mystery.
US Attorney Leah Foley in Boston said Valente, 48, was dead.
He had been a PhD student in physics who was familiar with the building where the shooting took place, officials said.
Providence police Chief Oscar Perez and Rhode Island Attorney-General Peter Neronha, told reporters on Thursday night that Valente took his own life and investigators believe he acted alone.
Perez said a tip from a person who confronted Valente inside a bathroom on Brown's campus led police to a car he had rented from an agency in Massachusetts.
There, police were able to obtain store footage of Valente in which he was seen wearing the same clothing seen in footage from the Brown University shooting, and find his name on the rental agreement.
Ted Docks, the FBI's special agent in charge of the Boston office, told reporters the suspect's body was found in a storage unit in Salem, New Hampshire, where a large contingent of law enforcement officers descended on Thursday night.
Salem is about 30km north of downtown Boston.
Valente had rented the storage unit where his body was found, Neronha said.
He said investigators did not know why Valente carried out the shooting or why he chose to do so in the building he targeted.
"That is really unknown to us," Neronha said.
Foley, the top prosecutor in Boston, said at a media conference that investigators were certain Valente "murdered MIT professor Nuno Loureiro" on Monday, saying prosecutors had ample evidence linking him to the crime.
One official in Providence said it was believed Valente and Loureiro attended the same university in the Portuguese capital, Lisbon.
Foley said that once investigators have some understanding of Valente's motive, it would be shared with the public.
Students Mukhammad Aziz Umurzokov and Ella Cook were killed at the Ivy League school on Saturday and at least eight were wounded.
Although officials said earlier this week they did not see a connection between the Brown University rampage and the death of a Massachusetts Institute of Technology professor who was found fatally shot on Monday, they now believe the two events might be linked.
Loureiro was killed in his home in the Boston suburb of Brookline, Massachusetts, some 80km north of Brown's campus.
He was a member of the departments of nuclear science and engineering and physics as well as MIT's Plasma Science and Fusion Center.
Investigators in Providence said the suspect in the Brown University shooting escaped on foot into nearby streets, prompting a search that relied heavily on residential security footage because of a lack of surveillance cameras in the classroom building and surrounding area.
Police released images and video of a masked man believed to be the shooter, based on survivor accounts, and have repeatedly asked for the public's help in identifying him.
Authorities initially announced a person was in custody a day after the shooting, but later released that individual after determining he was not involved.
