On the early morning of September 17, 2016, a house party on the 13000 block of Monaco Way in Thornton, Colorado, ended in gunfire that killed 16-year-old Haley Vargas. Witnesses said a disturbance at the party prompted people to run to their cars when a gunman opened fire; Vargas was struck in the torso in the street and later pronounced dead at a local hospital.

Witness descriptions given to police identified a skinny Hispanic male in his late teens or early twenties, about 5 feet 6 inches tall, with dark hair, glasses and a gold hoop nose ring, last seen in a gray sweatshirt. Investigators also sought information about two vehicles of interest: a black SUV (possibly a Chevy Tahoe, GMC Yukon, or Cadillac Escalade) and a red 4-door sedan from the early to mid-1990s. No arrests were made for several months.

In April 2017 an Adams County grand jury indicted 17-year-old Angelo Alvarez on charges including first-degree murder and attempted murder with extreme indifference; the district attorney elected to charge him as an adult. If anyone was at the party or saw the vehicles or suspect that night, please come forward with information.