FORT WORTH, Texas — Fort Worth police are investigating a quadruple homicide Friday night on the city’s south side in which four people were shot inside a car. In a statement early Saturday morning, police said three people died at the scene. The fourth was taken to a hospital but did not survive his injuries. Homicide detectives are investigating the case as a possible robbery involving drugs. No arrests have been announced. No names or ages of the victims have been released, though witnesses told the Star-Telegram that they appeared to be young men. The 911 call came in just before 7 p.m. in…