Authorities on Thursday night identified a 48-year-old man from Portugal as the suspect behind a deadly campus shooting at Brown University and the fatal killing of a professor affiliated with the Massachusetts Institute of Technology, bringing an end to days of uncertainty surrounding two violent incidents that shook the academic community in New England.

The suspect, Claudio Manuel Neves Valente, was accused of killing two students and wounding nine others during a shooting on Brown University’s campus in Providence, Rhode Island, last Saturday, according to the city’s police chief. After the attack, he managed to flee the campus and remained at large for several days, prompting an intensive multi-state manhunt.

While authorities were searching for him, Mr. Neves Valente traveled to Brookline, Massachusetts. There, on Monday, he fatally shot an MIT professor at the professor’s home, according to the U.S. attorney’s office in Massachusetts. The killing raised alarm across academic institutions, particularly given the apparent connection between the suspect and both universities.

Police later discovered Mr. Neves Valente’s body inside a rented storage unit in Salem, New Hampshire. Officials said on Friday that he had died from a self-inflicted gunshot wound approximately two days before his body was found, effectively ending the search.

As investigators pieced together his background, a complex portrait of the suspect began to emerge.

Mr. Neves Valente had a brief academic history at Brown University. He enrolled as a graduate student in physics in the fall of 2000 but took a leave of absence in April 2001. He formally withdrew from the program in 2003. During his time on campus, he likely spent considerable time in Barus and Holley, the physics complex where the shooting later took place. University officials said there was no evidence suggesting that he personally knew the two students who were killed or the nine individuals who were injured in the attack.

A former classmate from Brown’s physics doctoral program recalled that Mr. Neves Valente was quiet and socially withdrawn, and that he struggled academically despite his earlier promise. The classmate described him as introverted and largely disconnected from the broader student community.

Born and raised in Portugal, Mr. Neves Valente entered the United States in 2000 on a student visa, arriving through Boston Logan International Airport. Years later, in 2017, he became a lawful permanent resident of the United States, according to federal records.

Before his time in the U.S., Mr. Neves Valente had been regarded as a standout student. In the 1990s, he studied physics at Instituto Superior Técnico in Portugal, one of the country’s most prestigious institutions for science and engineering. He attended the school alongside Nuno F. G. Loureiro, the MIT professor who was later killed. The university said Mr. Neves Valente graduated at the top of his class.

Dr. Loureiro, 47, was found with gunshot wounds in his Brookline home on Monday night and was pronounced dead early Tuesday morning. Leah Foley, the U.S. attorney for Massachusetts, said investigators believed the suspect and Dr. Loureiro were acquainted, though she did not provide further details about the nature or depth of their relationship. Colleagues at Instituto Superior Técnico remembered Dr. Loureiro warmly, describing him as a respected scientist and mentor, but said they had no recollection of Mr. Neves Valente from that period.

Despite his early academic achievements, those who knew Mr. Neves Valente described his adult life as deeply troubled. After moving to the United States to pursue graduate studies, he gradually distanced himself from his family and eventually cut off all communication, according to Mirita Domingues, a relative of his parents.

Scott Watson, a physics professor at Syracuse University who studied alongside Mr. Neves Valente at Brown, said he was likely the suspect’s only close friend during that time. In an email sent Friday, Professor Watson said Mr. Neves Valente could be kind, gentle, and intellectually gifted. At the same time, he recalled that his former classmate often seemed unhappy and, at times, exhibited bullying behavior toward others.

Officials said Mr. Neves Valente’s last known address was located in a residential area north of Miami, Florida. Records also show that while he was enrolled at Brown, he maintained a residence in Providence, Rhode Island.

Investigators revealed that on December 1, Mr. Neves Valente rented a Nissan Sentra in Boston and drove it to the Brown University campus. Law enforcement officials said he took unusually sophisticated measures to conceal his identity, including altering the vehicle’s license plate and using a phone configured to mask his location. After the killing of Dr. Loureiro, authorities said he drove the rental car to the storage facility in Salem, New Hampshire, which he had previously rented.

A key break in the case came from an unexpected source. A post shared on Reddit drew attention to a suspicious vehicle, which ultimately helped guide investigators toward the suspect. The individual who made the post later contacted law enforcement directly, reporting an encounter with a man he found suspicious while on the Brown campus.

Inside the storage unit where Mr. Neves Valente died, investigators found at least two firearms, according to a person briefed on the investigation who was not authorized to speak publicly. The weapons were believed to be consistent with those used in both the Brown University shooting and the killing of Dr. Loureiro. Authorities said the firearms would undergo ballistic testing to confirm whether they matched the bullets recovered from both crime scenes.

Despite the growing body of information about the suspect’s movements and background, investigators acknowledged that the motive behind the attacks remains unclear.

“There are still many unanswered questions,” said Peter F. Neronha, the attorney general of Rhode Island. “Why Brown was targeted in particular is something we still do not fully understand.”

As the investigation continues, both Brown University and MIT have pledged to support their communities as they grapple with the aftermath of the violence, mourning the victims while seeking answers to how such a tragedy unfolded across institutions dedicated to learning and discovery.