HOUSTON, Texas (KTRK) -- Police are investigating a car crash that killed a teenage girl in southwest Houston.Officers say the accident happened just before 5 p.m. Sunday.The family of four was on their way to a movie theater.While stopped at a red light, their lives would be changed forever.A car slammed into their sedan, killing a 17-year-old girl. Her 13-year-old sister's arm was broken.The girls' parents were in the front seat. Their father was critically injured and their mother sustained minor injuries.The driver who hit them -- at what appeared to be a high rate of speed -- was behind the wheel of a Mustang. His 2-year-old son was in a child seat.Police said he grabbed his son and ran for several blocks. A wrecker driver saw him and told officers where to find him. The driver, who's in his mid-20s, is said to have failed a field sobriety test.A DRE team, which specializes in alcohol and drug impairment investigations, took him into custody for additional testing. The suspect's son was taken to a hospital as a precaution, but did not appear to have been injured, according to police.The girls' aunt and uncle came to the crash scene, calling their late niece "an angel." The tragedy, they said, was that their parents had tried for years to have children. Fertility treatment gave them two beautiful daughters.Now, one is gone.The suspect's car was not stolen, but it had no registration, and had what police called fake paper plates.Authorities did not release the name of the suspect or the victims.