PHILADELPHIA -- Police say a Philadelphia college professor killed himself by diving over a second-floor railing inside a campus building during class.

The Philadelphia Daily News reports that the instructor was Rudolf Alexandrov, an adjunct professor who taught math at Chestnut Hill College.

The newspaper says the 71-year-old professor walked out of his class Wednesday, returned briefly, yelled and then ran to a second-floor railing outside the classroom. Police say campus security was summoned and Alexandrov dived over the railing and hit the floor, some 20 to 30 feet below.

Lt. Robert Zaffino, a Philadelphia detective, says Alexandrov had had a history of depression and had been having suicidal thoughts.

The private four-year college canceled classes and made counselors available to students and others.