SPRINGFIELD, Pa. (WPVI) -- One suspect is in custody after a stabbing on a SEPTA bus in Delaware County.The incident happened around 3 p.m. Wednesday on Baltimore Pike at Church Road in Springfield.The 78-year-old suspect is being held at the police station.Authorities believe the stabbing was completely random, and the victim and suspect did not know one another.The SEPTA bus was making a stop when police say the 78-year-old rushed from the back of the bus and stabbed an 18-year-old passenger in the neck and head as the teen was getting off the bus.The victim was taken to Crozer-Chester Medical Center with nonlife-threatening injuries."Totally unprovoked, they weren't even sitting in the same section of the bus, they were on totally separate sections of the bus. The witnesses were shocked with what they saw. They didn't believe that they just witnessed that. After the stabbing, the (suspect) just sat back down on the bus and waited," Springfield Police Chief Joe Daly said.A Widener University security officer on the bus held the 78-year-old suspect until police arrived.They believe the suspect suffers from mental health issues.