HOUSTON,Texas (KTRK) -- A northwest Harris County man is on the run after allegedly killing his estranged girlfriend Sunday evening.According to court documents, Carlos Gonzalez, 26, called 911 and told the dispatcher she was either playing with the gun or cleaning it, and accidentally shot herself. Investigators say he then dropped their infant off on a relative's doorstep before going on the run.He's believed to be a member of the gang MS-13.The shooting happened Sunday evening inside their apartment at the Abbey at Champions Apartments. Maritza's mother, Blanca Garcia, told ABC13 the night before she was killed, she and Gonzalez, had an argument and that day she threw out his things.Garcia said Gonzalez had threatened to kill Maritza if she left him. She believed he made good on that threat.According to court documents, neighbors heard two people arguing, and then a loud boom. Investigators say he called 911 and left. They say he dropped their 3-month old daughter on a relative's porch, and he's been on the run since.Blanca Garcia said it's important to tell her daughter's story because she doesn't want other girls to end up like Maritza. She wants them to leave before it's too late.Gonzalez is an El Salvadorian national. Her family doesn't know if he's headed back home, there already, here in Houston hiding out, or in Miami where he has connections.There is a $5,000 reward for information leading to his arrest.If you would like to help, the family has set up aaccount to help cover funeral expenses.