A decades-old homicide case that remained open in spite of the identification of the shooter has officially been closed.

Mark Biggerstaff was shot to death in 1974 after trying to force his way into a his mother-in-law’s private residence, where his estranged wife was staying at the time. He reportedly gained access to the residence by smashing through a living room window, armed with a knife.

According to Bellevue police, the protection of a male family friend had been sought after Biggerstaff had made repeated threats toward his wife and her mother. After Biggerstaff had forced his way into the home, he was confronted by his wife’s male friend. Biggerstaff refused commands to stop, and was then shot with a rifle.

The Bellevue Police Department arrested the shooter at the residence that evening. The King County Prosecutor’s Office reviewed the case, but declined to file charges, as the shooting was determined to be in self-defense.

Why the case remained open for 40 years was unclear.

“The stated case is 42 years old and at some point it was put on the cold-case list, so we don’t have an answer as to why it was not listed as closed back in the 1970s,” the department said in a statement. “This is one of the reasons and benefits of why [the department] assigned a cold-case detective to review the cold-case homicides to determine the status of these cases, which led to the disposition of the Biggerstaff case.”

Biggerstaff’s death was one of seven open homicides and 10 missing persons cases assigned to Bellevue Detective Jerry Johnson.

After the department’s success solving the 1980 murder of Susan Lowe in 2013, they decided to revisit their open cases.

“While time can often be a disadvantage, sometimes it can also be an advantage,” Major Pat Spak said after Johnson’s appointment in January.

This is the department’s second cold case closed this year. Last month, the murder of Loren Sundholm — the city’s first homicide — was officially solved by another police detective.