A 20-month old boy and his mother were killed in a crash early Friday that left another person injured in suburban North Chicago.

Police were called at 2:06 p.m. to the intersection of Waukegan and Buckley roads where a crash was reported between a Nissan Rogue and a semi truck, according to North Chicago police and the Lake County coroner’s office.

The semi was heading south on Waukegan and stopped in the right-turn lane to head west on Buckley when it was struck from behind by the SUV, police said.

The driver of the Nissan, 25-year-old Cristina Mier of Lake Forest, was pronounced dead at the scene, the Lake County coroner’s office said. Her 20-month-old son was taken to Northwestern Medicine Lake Forest Hospital, where he also died.

Autopsies Monday found both Mier and her son died of multiple traumatic injuries they suffered in the crash, the coroner’s office said. Toxicology results were pending.

A 27-year-old passenger in the Nissan was taken in good condition to Condell Medical Center in Libertyville, authorities said.

“Our sincerest condolences go out to the family of Ms. Mier,” Lake County Coroner Dr. Howard Cooper said in a statement.