The gunman who shot three people at a library on Florida State University’s main campus in Tallahassee early Thursday was an alumnus who said the government was watching him, and he detailed his fears in a written journal and videos, the authorities said.

The suspect, whom the police identified as Myron May, 31, reloaded his gun at least once before he was killed by the police during an exchange of gunfire outside Strozier Library, near the center of campus, the authorities said during an afternoon news conference. The Tallahassee police chief, Michael DeLeo, said Mr. May kept a written journal and made videos expressing his fear of being watched by the government and his desire to bring attention to the issue.

“Based on our initial review of the documents and his videos and his postings, it’s clear that Mr. May’s sense of being and place in our community was not what most people would refer to as normal,” Chief DeLeo said. “He had a sense of crisis, and he was searching for something.”