An old friend of Claudio Manuel Neves Valente — who described himself as his only friend from his time at Brown University — said he was “shocked” to learn that Neves Valente is believed to have shot and killed two students at Brown last week.

Still, upon reflection, fellow Brown student and now Syracuse University professor Scott Watson remarked the the signs were there.

Authorities say Neves Valente opened fire in a classroom on the Brown campus on Dec. 13. Two students — Ella Cook and MukhammadAziz Umurzokov — died, and nine were injured. Neves Valente is then believed to have driven to the Boston area and then shot and killed MIT professor Nuno Loureiro in his Brookline apartment building.

Watson, now a professor of physics at Syracuse, got to know Neves Valente during their time together as students at Brown in 2000.

In an email to MassLive, Watson said he was surprised when he heard authorities identify Neves Valente as the killer.

Watson described Neves Valente, a native of Portugal, as a student who struggled to fit in at Brown, culturally and academically.

“He was socially awkward, and so was I, which I think is why we connected,” Watson said. “During orientation he was sitting alone, and I walked up and said hello. He was terse at first, but we eventually broke the ice and became close.”

Watson said he has “fond memories” of having lunch with Neves Valente at Portuguese restaurants near campus, but that Neves Valente often returned to grievances about schoolwork and campus life.

“He could be kind and gentle, though he often became frustrated — sometimes angry — about courses, professors, and living conditions,” Watson said.

In an interview with CNN, Watson said Neves Valente thought he had wasted his time by coming to the United States. “He hated Brown and he hated Providence,” Watson said.

Watson said Neves Valente was a brilliant student who bristled at coursework he believed to be beneath his level of intellect.

“He often complained about moving to the United States and about the university,” Watson said. “He would say the classes were too easy — honestly, for him they were. He already knew most of the material and was genuinely impressive.”

Neves Valente was also capable of agitating fellow students due to his standoffish personality.

Watson recounted how Neves Valente used to bully a classmate, a native of Brazil, often calling him a “slave.” Things escalated to the point Watson said he had to break up a fight between the two.

Neves Valente attended Brown in the fall of 2000 and spring of 2001. He then took a leave of absence, and eventually withdrew from the school for good in 2003.

Watson remembers his final conversation with Neves Valente, in which Watson tried to convince him not to leave the university. Neves Valente told him he was going to return to Portugal.

That was the final time Watson spoke with him, and the memories faded — until he heard Neves Valente’s name again when he was revealed as the Brown shooter.

“I am quite upset,” Watson said.

Authorities believe Neves Valente drove to a storage facility in Salem, N.H., after killing Loureiro on Monday, and then killed himself on Tuesday. His body was discovered in a storage unit on Thursday.

Speaking to CNN, Watson said he now realizes the signs were there when he was friends with Neves Valente.

“To me, he was sweet, nice and caring,” Watson said. “I never thought he would do something like this. But then in talking with the FBI today and to many journalists, I realize it was there.”