FEDERAL WAY, Wash. (AP) _ A man who moved to Idaho and led a ''pretty low-key'' life after his wife and sons disappeared 12 years ago has been arrested in their slayings, police said.

Mark James Bender was picked up late Thursday in Nampa, Idaho. Investigators traced him after the decomposed remains of his family members were discovered in a rented storage room in this Seattle suburb.

Bender first rented the 5-by-5 room on April 14, 1980, a day after he told a friend that his wife, Barbara, and sons had left him, according to court documents filed in support of an arrest warrant.

The remains of Mrs. Bender, 15-year-old Mark Jr. and 8-year-old Brian were discovered Wednesday by a man who purchased the room's contents sight unseen in an auction held Tuesday by the storage company after Bender fell several months behind in his payments.

Bender, 50, worked as a used-car salesman in the Nampa area, said Nampa police Capt. Glendon Crawforth. Bender had been in the area at least since 1985 and had lived a ''pretty low-key'' life with a new wife, Crawforth said.

Bender's boss, Timbre Wolfe, said Bender was friendly but, ''He definitely did not tell us a lot about his past.''

A hatchet with what appeared to be blood and hair on it was found in the storage room wrapped in a white towel, said the King County Superior Court documents. All three bodies had head injuries consistent with hatchet blows, the records said.

Police looked into the disappearances of Mrs. Bender and the boys in 1980 and 1985 to no avail.

George Gennai, who bought the storage unit's contents, called police when he found the human remains wrapped in green plastic and bound with wire. Among household furnishings in the unit were documents and school records indicating the Bender family had lived in Seattle area from 1969 or earlier to 1980.

Bender was tracked to Idaho through canceled checks and financial records of the storage company.