Officers responded to a report of a man who was chasing people around the parking lot with a knife. Upon further investigation, it was determined that a person approached four people and threatened them with a knife. Witnesses stated the suspect began chasing the victims with the knife until he was detained by Union City Police. No one was injured, and the suspect was placed under arrest for brandishing a weapon in a threatening manner and for making threats. A sergeant arrived at the scene to approve the arrest and interview the suspect, who denied threatening anyone. The suspect was also issued a 30 day BART prohibition order. TSOC notified.