CHESTER, Maine -- State Police have released the identities of a mother and toddler killed in car crash on Interstate 95 north of Lincoln, Maine on Thursday in what police believe was a suicide.

Troopers said 26-year-old Heidi McGovern of Lee stepped in front of a tanker truck, holding her 2-year-old son, Enoch. Troopers said McGovern had left suicide notes behind at her home.

Department of Public Safety spokesperson Steve McCausland said McGovern was killed instantly and her son was thrown from her arms, away from the truck, and landed in the passing lane of the highway. The boy remains hospitalized at Eastern Maine Medical Center in Bangor with serious injuries.

He said the tanker truck is owned by Irving Oil, and was hauling fuel.

The crash took place about 4:30 p.m. in Township 2 - Range 8, which is about four miles north of the Lincoln exit.

McGovern was also the mother of an infant, who was elsewhere, at the time of the incident.