San Francisco police this week arrested a 51-year-old man for allegedly holding up a Tenderloin check-cashing store at gunpoint over the weekend, police said Friday. Gabriel Mosby allegedly robbed the store in the 400 block of Eddy Street on Saturday, and fled in an older-model, silver Mercedes-Benz S500, according to police. On Tuesday, officers spotted Mosby getting gas at a station at Third Street and Evans Avenue in the Bayview District and arrested him, police said. During a search of the vehicle, police found crack cocaine and black tar heroin — as well as “several thousand dollars in cash,” suspected to have been taken from the check-cashing store, in Mosby’s pockets, police said. A subsequent search of three homes in the Bayview uncovered additional evidence from the robbery and evidence allegedly connecting Mosby to another recent commercial robbery, according to police. Mosby was booked on suspicion of robbery, drug possession for sale and parole violation, according to police.