Portland police said a man who assaulted his girlfriend and jumped into the frigid waters of Back Cove and drowned on Sunday was having a mental health crisis.

Police said Eric Cohen, 25, had a history of mental health problems and became seriously distressed as he and his girlfriend walked down Marginal Way near the Miss Portland Diner about 1 p.m.

Police say that Cohen unexpectedly stripped off his clothes and, as his girlfriend began to pick up articles of his clothing and attempted to calm him down, Cohen beat her unconscious. Cohen only stopped after intervention by a bystander, who was also assaulted.

After the assault was interrupted, Cohen fled behind the diner and across I-295. He then jumped into Back Cove. Firefighters pulled him from the water 24 minutes later and transported him to Maine Medical Center. He was unresponsive and could not be revived, and he was pronounced dead at the hospital.

An autopsy to determine the precise cause of death was scheduled for Monday.

Police said that Cohen’s girlfriend was released from the hospital with minor injuries, and they credited the good Samaritan’s actions for saving her from further injury.

Reached Monday afternoon, the man who intervened in the assault said he did what anyone would do, despite suffering some injuries himself. But he said he did not want to be identified in the newspaper:

“I’m not very well liked, and I prefer to keep it that way,” he said.