An Ohio State University janitor who received a bad job evaluation shot two supervisors in a campus maintenance building, killing one of them, then fatally shot himself, officials said Tuesday.

Nathaniel Brown, 51, who was hired in October and was still on probation, arrived for work at the nation's largest university dressed in dark clothing, a hooded sweat shirt and a backpack, then opened fire in an office suite using two handguns, campus Police Chief Paul Denton said.

About a half-dozen other employees were in the building when the shooting began, he said. He described the shooting as work-related and said Brown recently received a poor performance evaluation, though he declined to say whether that was the motive.

No students were hurt, and classes went on as scheduled.

The shooting was first reported at 3:30 a.m. Tuesday. Police tactical units surrounded the building and found Brown with a self-inflicted gunshot wound in a garage bay, Denton said. He was pronounced dead at a campus hospital several hours later.

Brown had been scheduled to work his normal third shift, Denton said.

One of the victims, building services manager Larry Wallington, 48, died at the scene. The other, operations shift leader Henry Butler, 60, was in stable condition at Ohio State University Medical Center, officials said.

Denton declined to say whether other employees were targeted. Police also didn't describe the contents of Brown's backpack.

The other employees in the building at the time have been offered grief counseling, Denton said.

"This is a tragic event, and our hearts go out to all of the families," said Vernon Baisden, assistant vice president for public safety.

Police released two 911 calls. In one, a caller tells the dispatcher that he pulled into the garage and heard gunshots. He identifies Brown as the shooter and says Brown was in the process of being fired.

Ohio State spokeswoman Shelly Hoffman declined to comment on Brown's employment status, saying the issue remained under investigation.

It wasn't immediately clear whether the university had conducted a background check on Brown, who was released from prison in 1984 after serving about five years on a charge of receiving stolen property.

Ohio State's policy on background checks depends on the type of job position, Baisden said.

Both shooting victims had worked for the university for about 10 years. Family members reached Tuesday declined to comment.

Graduate student Kiernan Gordon, 31, said he found out about the shootings from his wife, who called him on his cell phone while he was driving to campus. He said he didn't have any concerns about his own safety.

"Ohio State is really a city unto itself, and like any city it has problems unto itself," Gordon said.

More than 55,000 students attend the university's main campus in Columbus. The maintenance building is next to a power plant and across the street from Ohio Stadium, home to the university's football team.

Click here for more on this story from Fox 28 in Columbus.