An apartment building manager says a popular San Diego college professor was overheard calling for help shortly before he was found slain in his Tijuana, Mexico, apartment, according to AP. Apartment manager Marcos Leon told the San Diego Union-Tribune Wednesday that a watchman had seen Henry Acejo enter his ground-floor unit with two men on Dec. 18. Leon says a neighbor called police after hearing Acejo shout and pound on his window, but by the time officers arrived, the two men were gone and Acejo was found dead. The Baja California Attorney General's Office said it did not yet have the results of Acejo's autopsy and gave no possible motive. Acejo was an instructor at Southwestern College in Chula Vista, San Diego State University and Mid-City Community College.