THORNTON, Colo. Four people were killed and another person seriously injured in a fiery two-vehicle crash in Thornton Saturday night.The crash occurred around 7:30 p.m. at the intersection of Thornton Parkway and Washington Street, according to the Thornton Police Department.Police said one of the two vehicles involved in the crash caught fire, killing all four occupants inside.The driver of the second vehicle was transported to the hospital with serious injuries.The cause of the crash is under investigation. Police did not release additional details.The Adams County Coroners Office will release the identities and the official cause and manner of the four deceased at a later time.