A couple and their 2-year-old son were found dead Wednesday in a parked car in the city of Noboribetsu, Hokkaido Prefecture, police said.
The police suspect the man from Muroran, Hokkaido, and his wife, both 23, killed themselves and their son because a suicide note and coal stove, commonly used by suicidal people to poison themselves with carbon monoxide, were found in the car.
The note says the couple had debt-related troubles with their relatives, the police said.