A semi-truck driver who plowed into stopped traffic near Denver, Colorado, on Thursday faces four counts of vehicular homicide, according to police. The fiery pileup involved four semi-trucks and 24 cars, resulting in four deaths. The driver has been identified as Rogel Lazaro Aguilera-Mederos, 23, a licensed commercial driver out of Texas. Aguilera-Mederos was injured in the crash but not seriously, and is reportedly cooperating with investigators. Aguilera-Mederos was transporting lumber at the time of the crash. According to his brother, Daniel Aguilera, who spoke to him after the crash, Aguilera-Mederos said his brakes failed. A police spokesperson told reporters the department is looking into whether there were any mechanical issues with the truck, adding that even if there was a mechanical issue, vehicular manslaughter charges would still be applicable.