A 4-year-old girl was the only survivor of a shooting rampage that left four people, including the gunman, dead at a home in central Maine, police said Thursday.

Officials received several 911 calls about a shooting at a home in Oakland, Maine at about 8 p.m. Wednesday, Department of Public Safety spokesman Steve McCausland said in a statement, adding that one of the calls was from one the victims, according to the Associated Press.

By the time the rampage ended, Amanda Bragg, 30; Michael Muzerolle, 29; and Amy Derosby, 28, were all found dead inside the home, reported ABC News. The gunman, who was identified as 42-year-old Herman Derico, was found dead in the driveway with a 9mm handgun next to his body.

The only person found alive was the girl, who was identified as Bragg's and Muzerolle's daughter. She is now in the custody of her grandmother.

Investigators are trying to determine a motive. McCausland said that detectives will talk to family and friends to try to understand what happened. 

Based on initial testimony from next-door neighbor Jason Thomas, the shooting may have been born from a domestic dispute.

Thomas reportedly heard a woman say, "Please, please don't!" before he heard two gunshots prompting him to call 911.

"[He] yelled something like, 'I told you this was going to happen,'" Thomas said. "And then I heard two more shots."

"The task that investigators have is to try to find out what sparked this violence, what set this man off," McCausland said, adding that Derico had no criminal record in Maine, according to The Boston Herald. "We have a lot more work to do before we're even close."