The man suspected of killing two students at Brown University and fatally shooting a Massachusetts Institute of Technology professor days later recorded a series of short videos after the violence that provided no clear motive and suggested he’d spent significant time planning, federal officials said Tuesday.

In transcripts of the videos released by the U.S. attorney’s office in Massachusetts, Portuguese national Claudio Manuel Neves Valente, 48, said he did not hate the United States and complained about an eye injury that he said he suffered from a shell round. He appeared to say he had been planning the violence for at least six semesters, and he said no one had ever sincerely apologized to him in his lifetime.

“The world cannot be redeemed,” he added, according to the transcripts.

The four videos were recovered from the New Hampshire storage unit where Neves Valente was found dead on Dec. 18, the prosecutor’s office said in a statement.

Authorities said he opened fire inside a Brown auditorium on Dec. 13, wounding nine students and killing two — Ella Cook, 19, an Alabama native and vice president of a college Republican group, and Mukhammad Aziz Umurzokov, 18, a native of Uzbekistan who relatives said dreamed of becoming a neurosurgeon.

Two days later, authorities said, Neves Valente fatally shot MIT professor Nuno Loureiro at Loureiro’s home near Boston.

In one of the videos he recorded, Neves Valente said he’d had previous opportunities to carry out a shooting at Brown but that he’d “always chickened out,” according to the transcripts released Tuesday.

The U.S. attorney’s office said an initial review of evidence showed Neves Valente targeted Brown, but it did not provide a motive for that shooting or that of Loureiro.

“Neves Valente showed no remorse during the recordings; on the contrary, he exposed his true nature when he blamed innocent, unarmed children for their deaths at his hand and grumbled about a self-inflicted injury he suffered when he shot the MIT professor at close range,” the office said in a statement.

Rhode Island’s attorney general credited a Reddit user who encountered Neves Valente at Brown and posted about it with providing crucial clues that helped authorities track him to the storage unit where he was found dead of a self-inflicted gunshot wound.

Neves Valente, whose last known address was in Miami, attended Brown in the early 2000s as a Ph.D. physics student before he withdrew in 2003, a university official has said. He also appears to have attended the same university in Portugal as Loureiro, a special agent in charge of the FBI’s Boston field office has said.

An investigation into a possible motive will continue, prosecutors said Tuesday.