A professor at Chestnut Hill College dove over a second-floor railing inside a building on campus during his class, killing him, police say.

Rudolf Alexandrov, 71, an adjunct professor teaching mathematics at the private four-year college, walked out his class Wednesday afternoon, returned for a moment, yelled some words and then ran to a railing overlooking the veranda, the Daily News reported.

When campus security was alerted and summoned, Alexandrov, who had been standing on a ledge next to the railing, dived head-first over the railing, hitting the marble floor about 20 to 30 feet below, said Lt. Robert Zaffino with Northwest Detectives.

Alexandrov jumped in front of his students and his 56-year-old wife, Olga Alexandrov, who also works as an adjunct professor at the college.

Philadelphia police have ruled it a suicide.

"He had a history of depression," Zaffino said. "He had been having suicidal thoughts and mentioned harming himself in the past."

On July 29, Alexandrov's wife reported him missing, and the police when to his home; he was found soon after walking around his neighborhood, Abington Police Deputy Chief John Livingood said.

The college canceled classes and made counselors available to students and others at the school.