The death of a 100-year-old SeaTac man last week is being investigated as a homicide, according to the King County Sheriff’s Office.

A close friend became worried Friday morning after Robert O. Benson missed a weekly coffee meet-up, according to sheriff’s spokeswoman Sgt. DB Gates. The two had been getting together for coffee on Friday mornings for more than 40 years, Gates said.

The friend went to Benson’s home to check on him and found his body, Gates said. The cause of death is undetermined, according to the Sheriff’s Office.

After detectives arrived they found that Benson’s wallet was missing, and the Sheriff’s Office is seeking more information on its whereabouts.

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The scuffed, brown leather wallet contained Benson’s driver’s license and credit cards from Chase, Key Bank and Discover, the Sheriff’s Office said. The wallet also contained Benson’s AARP card, proof of car insurance and Medicare card.

Gates declined to say whether Benson might have been killed during a robbery.

Benson had lived in his SeaTac home for decades. His family helped develop the residential neighborhood and he was well-known in the area, according to Gates.

“He still lived in that house independently. He was driving and able to get around on his own,” Gates said. “So it seems he was in very good health for 100 years old.”

Gates said Benson had a daughter in the Seattle area who is cooperating with the Sheriff’s Office.

The Sheriff’s Office is asking that anyone with information on the wallet or the suspected homicide call 206-296-3311.

Erin Heffernan: or 206-464-3249