EVERETT — An Everett man who told homicide detectives about a death pact he had with his girlfriend admitted Monday that he accidentally shot and killed the woman last year.

Donald Madsen, 63, faces nearly a decade in prison for the death of Pamela Placek, 52. Placek was found dead Sept. 24, 2008 inside a south Everett rental home the couple shared. Police believe Placek died immediately, shot in the face at close range.

Madsen told police the shooting was an accident. He told investigators he couldn’t remember pulling the trigger but he realized his girlfriend had been shot and called 911.

Madsen on Monday pleaded guilty to first-degree domestic violence manslaughter with a deadly weapon. He admitted that he recklessly caused Placek’s death. He is scheduled to be sentenced in February.

Madsen told detectives that the shooting happened while he was discussing a death pact with Placek. He told the detectives that he explained to Placek that the couple would be together forever. If one of them broke their vow, the other would be expected to load a specially painted bullet into a gun and shoot the other person.

Madsen said as he was trying to persuade Placek to agree to the pact when he grabbed a gun from the safe, court paper said.

He told investigators he didn’t remember anything else, court papers said. He said he must have pulled the trigger.

Detectives found a .45-caliber handgun next to Placek.

Investigators learned that Madsen was an experienced and well-trained gun handler. He’d taken several gun classes and taught gun safety training. Detectives found numerous books about weapons in his home. They also learned that Madsen was a member of Boeing’s gun club.

Madsen told investigators that he’d warned Placek to treat every gun like it was loaded, court papers said.

He speculated to detectives that he must have thought the gun was unloaded, Snohomish County deputy prosecutor Paul Stern wrote.

Madsen called his actions “total (expletive) idiocy,” court papers said.

Diana Hefley: 425-339-3463; hefley@heraldnet.com.