San Leandro police said they detained a 39-year-old man for a 72-hour mental health evaluation after an incident at a grocery store on Monday night in which he allegedly was armed with a pistol and was acting despondent. Police said they first were informed that the man was inside the Grocery Outlet store in the 2100 block of East 14th Street at about 7 p.m. on Monday and then were told that he was near the store and was still armed with a pistol.