PORTLAND, Maine - A 74-year-old man was charged in the shooting deaths of two of his tenants, possibly in a dispute about where they parked their cars during a snowstorm, state police said Sunday.

James Pak was arrested about 10 p.m. Saturday after a standoff at his home in suburban Biddeford, about 15 miles south of Portland, police said. He is charged with two counts of murder in the deaths of Derrick Thompson, 19, and Thompson's girlfriend, Alivia Welch, 18.

Thompson's mother, Susan Johnson, 44, called police to report the shootings about 7 p.m. She and her 6-year-old son also live in the apartment, which is attached to the main house where Pak lived.

Before the shootings, Biddeford police were called to Pak's home regarding a dispute between Pak and his tenants over their cars being parked in his driveway during the snowstorm, said state police spokesman Steve McCausland. Biddeford had banned street parking during the night so city crews could plow.

Minutes after officers left the home, they received the call reporting the shootings. Upon their return, police rescued Johnson and her young son, and Pak retreated to his part of the house, where he lived with his wife, McCausland said.

Pak's wife left the home, and he surrendered hours later after talking to police negotiators, said McCausland. A gun was found in the house.

Johnson was being treated for a gunshot wound at a Portland hospital, officials said. Her younger son was not hurt.

Detectives are investigating whether the violence stemmed from a landlord-tenant dispute, McCausland said.