(CNN) A man who police say opened fire on a Dallas federal building was possibly suicidal and had spent time in a mental institution, his parents told The Dallas Morning News.

Federal law enforcement fatally shot Brian Clyde on Monday before he was able to enter the Earle Cabell Federal Building, authorities said. No one else was seriously injured in the shooting on the south side of the downtown building housing about 300 federal workers, a prosecutor said.

Clyde's father, Paul, told the Dallas newspaper Wednesday that he suspects his son "went down there purely for suicide by cop." He called it a gut feeling and said he didn't know what might've driven his boy "over the edge."

"We had discussions of suicide thoughts in the past," he told the paper, explaining the most recent conversation came Saturday.

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