Brockton, Mass. — A Massachusetts man who told police he was exorcising a demon and performing a baptism when he shoved his father's head under water multiple times has been convicted of involuntary manslaughter in his death.

A jury found Jack Callahan, 22, guilty on Thursday, following an eight-day trial. Callahan is scheduled to be sentenced on May 3.

In June 2021, police in Duxbury got a call that Callahan, then 19, was behaving erratically and that his father, Scott Callahan, 57, was missing near a pond in a park.

Prosecutors said police found Jack Callahan at a home distraught and hyperventilating. Fire department officials found Scott Callahan submerged in the pond at about the same time. He was later pronounced dead at a hospital.

Investigators said the younger man was at first trying to help his father, who had left a center where he was being treated for alcohol abuse. The two took a ride-share vehicle from Boston to the area of the pond. The two began fighting, prosecutors said.

Scott Callahan's cause of death was drowning, and the manner of death was homicide, prosecutors said.

Jack Callahan, who was charged with murder, pleaded not guilty. He told police back in 2021 that he believed his father was possessed by a demon and he needed to be baptized and exorcised, investigators had said. That information was not included in Callahan’s trial, according to The Patriot Ledger.

Callahan’s attorney had called the investigation “shoddy." He said the state didn’t have enough evidence to convict Callahan.