GORHAM, Maine — Maine state police have determined that the fiery deaths of a mother and her 12-year-old son at a gravel pit in Gorham were a murder-suicide.

Detectives say 41-year-old Karen Devine of Windham doused her sport utility vehicle with a flammable liquid before setting it ablaze as she and her son, Michael, sat inside. The bodies, burned beyond recognition, were discovered after firefighters extinguished the blaze early on Aug. 19.

Detectives say that the day before the deaths, Karen Devine sent letters to family and friends containing money, household budget information and burial instructions for Michael.

Detectives classified Michael Devine’s death as a homicide and Karen Devine’s as a suicide. Their only survivor was Dr. John Devine of Windham, who practices in Manchester, N.H.