BOSTON — The man identified by law enforcement as the shooter who killed two Brown University students and an MIT professor had been planning the attack for at least six semesters, according to information released Tuesday by the U.S. Department of Justice.

Claudio Neves Valente, 48, a former Brown student and Portuguese national, was found dead in a New Hampshire storage facility after he killed two students and wounded nine others in an engineering building on Dec. 13. Two days later, he killed MIT professor Nuno F.G. Loureiro in his home in the Boston suburb of Brookline.

Justice Department officials said Tuesday that during the search of the storage facility where Neves Valente’s body was found, the FBI recovered an electronic device containing a series of short videos made by Neves Valente after the shootings.

In the recordings, the shooter admits in Portuguese that he had been “planning the Brown University shooting for a long time,” according to a news release. He did not provide a motive for targeting Brown or the MIT professor, with whom he attended school in Portugal decades ago.

He said he felt he had nothing to apologize for. He also complained in the videos about injuring his eye in the shootings.

“I’m not going to apologize because during my lifetime no one sincerely apologized to me,” he said.

Neves Valente said his “only objective was to leave more or less” on his “own terms” and to ensure he “wouldn’t be the one who ended up suffering the most from all this.”

“No, that cannot happen. So if you don’t like it, tough luck,” he said. Neves Valente called his execution of the murders “a little incompetent.”

“But at least something was done,” he said.

In the recording, he said he’d had the storage space where his body was found for about three years.