A Houston car mechanic was shot and killed Friday over a $500 charge for fixing a client’s truck, reports said. Luis Manuel Casillas, 29, apparently fought with the suspect—who police have yet to identify—over the bill before the shooting began. Casillas’ family pleaded Monday for the public’s help in identifying the murderer, who they believe is a young man. Casillas’ sister Sandy said authorities have six suspects, but police haven’t yet released an official description of the assailant (or assailants). Casillas leaves behind a wife and two daughters, aged 2 and 3. He was going to use the money from fixing the truck to finish buying their last Christmas gifts, his sister said. “Santa was coming with daddy. Santa showed up, but daddy didn't,” she told ABC13 during an emotional interview.