PROVIDENCE, R.I. (AP) — Just before Thanksgiving, Claudio Neves Valente checked into a Boston hotel and traveled to Brown University, where he had studied physics 25 years earlier. The drive to Providence was short, and in the days that followed, the 48-year-old Portuguese national returned to the campus again and again. On most trips, he drifted around Brown and the surrounding neighborhoods in a gray Nissan rental car with Florida plates. A custodian noticed him inside an engineering building while most students were home on the holiday break and spotted him again three days later, according to authorities.

Investigators say that on Dec. 13, Neves Valente returned to Brown once more, this time with a 9 mm handgun, and he opened fire in a lecture hall in an attack that killed two students and injured nine others. He got away in the ensuing chaos and two days later showed up at the home of a Massachusetts professor who was a classmate of his in Portugal in the 1990s, and fatally shot him, too, investigators said.

In their frantic search for the Brown attacker, authorities released footage in the hopes that someone might recognize him. But his face was always hidden behind a mask, with a black beanie covering his head. “I wish the video could speak, and then I’d have the answers I need,” a frustrated Providence police chief, Col. Oscar Perez, told reporters during one of the week’s news briefings.

Investigators are still trying to figure out much of what Neves Valente was doing in New England in the weeks before the shooting, but they know he repeatedly visited the Ivy League school’s Providence campus. He was spotted on surveillance footage at a Boston rental car agency as early as Nov. 17. Neves Valente, who attended Brown as a graduate student during the 2000-01 school year, may have arrived in Boston from Miami, the site of his last known address.

Last Saturday, he roamed the streets near campus for hours, sometimes jogging and sometimes walking with what investigators described as a distinct gait. At about 4 p.m., authorities believe Neves Valente entered the engineering building through the street-facing door, walked into the lecture hall and opened fire on students who were studying for a final before slipping away.

On Monday night, shots rang out in a neighborhood in the Boston suburb of Brookline, where someone had shot MIT professor Nuno F.G. Loureiro in his home before fleeing. Loureiro, a physicist who ran one of MIT’s biggest labs, grew up in Portugal and studied in the same university program as Neves Valente.

While trying to find an image of the Brown attacker’s face in the days after the shooting, investigators were also interviewing the students who were in the room when he opened fire. As the details unfolded, it became clear that the ties between the two attacks raised more questions while investigators worked tirelessly to find connections and motives in this harrowing series of events.