Officers responded to the station on a report of an armed man who had run to the platform. On arrival, officers determined that a security guard had chased an armed robbery suspect to the station from a nearby store and El Cerrito PD officers were already on scene. The suspect was located on the platform and a replica firearm was recovered along with a knife. The suspect was arrested by El Cerrito PD. Trains were delayed for several minutes during the search for the suspect. TSOC notified TSA-05-14684-16.