Loureiro was shot in the foyer of the apartment building where he lived in
Brookline, Massachusetts, on the evening of 15 December 2025. He was transported to
Beth Israel Deaconess Medical Center in Boston with gunshot wounds, where he was pronounced dead early on 16 December. Authorities opened a
homicide investigation that received widespread publicity. Portugal's Minister of Foreign Affairs
Paulo Rangel announced his death to the
Parliament of Portugal. The president of Portugal,
Marcelo Rebelo de Sousa, issued a statement calling his death "an irreplaceable loss for science", and the U.S. ambassador to Portugal released a statement with condolences. MIT president
Sally Kornbluth published a message to the MIT community, and professors from across the university made public remarks regarding Loureiro's life and work. A vigil was held by his home in Brookline. On 18 December, authorities announced that they were investigating a link between Loureiro's murder and the
shooting at Brown University two days prior that killed two and injured nine. Authorities confirmed the link later that day at a press conference announcing the suicide of the lone suspect in the Brown University shooting, Cláudio Manuel Neves Valente, a Portuguese national. The Connecticut State Police Forensic Science Lab confirmed that one of the firearms found with Valente matched the weapon used in Loureiro's murder. Valente attended the
Instituto Superior Técnico with Loureiro from 1995 to 2000, graduating first in his class, ahead of Loureiro. Later that same day, authorities found Valente dead of a self-inflicted gunshot inside a storage unit in
New Hampshire. As of April 2026, the killing of Loureiro is under investigation as part of a
White House probe into people with high government clearance and
scientists who have died or gone missing in recent years, including
Monica Jacinto, a
materials engineer at
NASA's
Jet Propulsion Laboratory, retired Air Force Major General
Neil McCasland, and
Caltech astronomer
Carl Grillmair, among others. ==Personal life==