Mountlake Terrace police are investigating the death of a 29-year-old woman allegedly assaulted by a man during an argument at a home in the 23600 block of 53rd Avenue West early Monday morning.

Police responded to the home after a man called 911 to report he had hit his deceased son’s girlfriend and that she was lying unconscious in the driveway. Arriving officers found a 29-year-old Mountlake Terrace woman dead in the driveway with massive trauma to her head.

The 43-year-old man living at the home told police officers that the woman had come to the home to collect some of her belongings. During that time, the two discussed the drug overdose death of the man’s son, who was the woman’s boyfriend.

“They allegedly argued and he struck her with a bat-like object,” a police news release said.

The 43-year-old man was arrested and booked into the Snohomish County Jail for second-degree murder.

Deputy Chief of Police Pete Caw said police believe the woman had been living at the home, but hadn’t been present for several days.

The Washington State Patrol Crime Lab is assisting with the investigation, Caw said.