A 3-year-old boy killed Sunday in a hit-and-run crash on a Florida interstate was sitting unrestrained in a passenger’s lap instead of a child seat, authorities said.

The crash occurred on the eastbound I-4 in Polk County around 2 p.m. when a white sedan hit the 2011 Nissan carrying the victim, the Florida Highway Patrol (FHP) said.

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The boy, identified as Josiah King, was one of five people in the vehicle when a white sedan merged from the left lane and struck the left rear side of the Nissan driving in the center lane, the Orlando Sentinel reported, citing the FHP.

Josiah’s 21-year-old mother, Yahkirioth Swain, lost control of the vehicle and hit the guardrail at the center median, according to local reports.

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The 3-year-old, who was on the lap of a passenger in the backseat, died of his injuries at Lakeland Regional Health Medical Center, WFLA-TV reported. Swain and the other passengers, ages 7, 14, 17, and 27, were all wearing their seatbelts and suffered minor injuries.

The driver of the sedan failed to stop following the crash.

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Investigators have asked anyone with information to call the FHP at 813-558-1800 or Heartland Crime Stoppers at 800-226-8477.