Updated 8:25 p.m. Tuesday
BART police are investigating a Tuesday afternoon incident in which they say a fight between two men on a train ended with one fatally stabbing the other.
Ed Alvarez, BART's interim police chief, told reporters that the alleged assailant fled a Warm Springs train after it stopped at South Hayward Station. Alvarez said the suspect was arrested nearby by Hayward police officers.
Alvarez said that the two men began fighting shortly after the southbound train left Bay Fair Station. Eventually, one of the men pulled a knife and stabbed the other, Alvarez said. BART police responding to South Hayward found the victim, who was pronounced dead aboard the train.
Neither the victim nor the suspect were identified, though Alvarez said both men appeared to be in their 40s.