A 22-year-old man was arrested Friday in the deaths of three family members whose bodies were found in their burned-out home in Orchard Beach, state police said.

Matthew Cushing was charged with three counts of murder and one count of arson in the stabbing deaths of his mother, Carol Bolduc, 42; his stepfather, Christopher Bolduc, 42; and his half-brother, Joshua Bolduc, 15.

The Wednesday night fire was immediately described as suspicious and the state fire marshal's office said Friday that it was deliberately set.

Investigators said fires were started in the kitchen, hallway and basement stairway of the Cape Cod-style home and a melted plastic gas can was found on the kitchen floor.

Cushing had been staying with relatives in Lincoln County and was arrested after being brought to the sheriff's office in Wiscasset for questioning. He was being held in the York County Jail pending an initial appearance Monday in York County Superior Court.

Cushing was a student at the University of Maine but had taken the semester off, police said.

Christopher Bolduc operated two novelty shops near the Old Orchard pier in this summer resort town, which has a year-round population of 9,000. The family lived in a fairly new residential neighborhood near a golf course, and Carol Bolduc was president of the neighborhood association.