A Chestnut Hill College professor did the unthinkable Wednesday afternoon during math class.

Rudolf Alexandrov, 71, an adjunct professor, became agitated and quickly walked out of the classroom inside St. Joseph's Hall, according to sources familiar with the incident. He returned briefly, then yelled some words and ran to the second-floor railing overlooking the veranda inside the hall.

When concerned colleagues summoned campus security, Alexandrov, who had been standing on a ledge next to the railing, dove head-first over the railing, said Lt. Robert Zaffino, with Northwest Detectives. The fall to the marble floor is about 20 to 30 feet, he said.

The horrific act reportedly took place in front of his students and wife Olga Alexandrov, 56, also an adjunct professor at Chestnut Hill, according to sources.

The tragic sequence of events remained a mystery yesterday.

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

Abington Township police had visited his home in Elkins Park July 29 after his wife filed a missing-person report, said Abington Deputy Chief John Livingood. Alexandrov had been missing for an hour and was found walking in the neighborhood shortly after police were called, Livingood said.

The college released a statement on its website, but a spokeswoman yesterday would not acknowledge specifics of the case until the police investigation is completed.

"President Carol Jean Vale, SSJ, Ph.D., and the entire Chestnut Hill College community wish to express our deepest sympathy to the family of adjunct professor Rudolf Alexandrov who died in a fall at the College on August 3," the statement read.

The school is offering counseling to those who witnessed the incident. Classes were held yesterday.

Neighbors of the Alexandrovs expressed shock. They said the Alexandrovs kept to themselves, but greeted others when they were out walking their dog.