The driver of a Tri-Delta Transit bus reported that a Black male, 40's, tall, thin, would not exit the bus at the end of the route. The driver left the bus and returned a short time later to find the male apparently masturbating under his clothing. The driver exited the bus, but the male chased the victim to a nearby business where she locked herself inside a restroom. Brentwood PD officers responded and detained the suspect. BART officers arrived and conducted a records check on the suspect. The suspect was found to be on court probation. The bus driver positively identified the suspect who was then placed under arrest upon a citizen's arrest by the driver. The suspect was transported to the Martinez Jail for lewd conduct and a probation violation.