HOUSTON, Texas (KTRK) -- Police are investigating after they say a violent ex-boyfriend shot up the car his ex-girlfriend and her new boyfriend were riding in.Officers were called to the 4000 block of South Post Oak around 2 a.m. Friday after a woman said her vehicle had been shot at.The victims told police that the driver's ex-boyfriend blasted their vehicle with four bullets, forcing them to stop for help along South Post Oak and the South Loop.According to police, the new boyfriend was shot once in the backside, while sitting in the passenger seat. He was transported to the hospital in stable condition.