19-year-old Eric Niles was pulled over by police in Norwalk, Connecticut after a chase on the interstate.
Niles shot himself in the head while sitting in the passenger seat when officers approached the truck.
Officials say that he’s in grave condition.
The driver of the truck was 18-year-old Kristin Cates of Bradley.
Maine detectives are on their way to Connecticut to interview her.
Niles had been wanted for questioning in connection with a stolen truck, and the death of 20-year-old Blake Mishou of Greenbush.
Mishou’s body was found at the home of Kristin Cates’ parents in Bradley Sunday morning.
Police won’t say how Mishou died, though they have ruled the death suspicious.
Mishou’s body is at the medical examiners office for an autopsy, which will take place on Tuesday.