An unknown witness called to report a Robbery in progress at the station. The witness described two black male suspects, one robbing a Hispanic male victim at gunpoint and possibly boarding a San Francisco bound train. BART Officers checked the train at Powell Street Station and asked two subjects that matched the suspects’ description to off-board the train. When the suspects off-boarded they each went in different directions. One officer detained one of the suspects and the other officer chased after the other suspect. The suspect tossed a black handgun before he was apprehended on the platform. Both suspects were determined to have warrants from the Dept. of Corrections, one for robbery and one for burglary. The original R/P for this report was not located and the victim never reported the crime. The officers were unable to substantiate a robbery charge but one of the suspects had suspected cocaine in his possession, as well as what turned out to be a replica handgun. Both suspects were arrested for their warrants and one of the suspects was further charged for drugs and a replica handgun. Detectives were called out to interview the suspects. Both of the suspects were booked at the San Francisco County Jail.