The robber also pointed a gun at White Center Shell station owner John Henry.
Sgt. John Urquhart says officers quickly identified a suspect from tips received after surveillance video of Saturday's robbery "went viral."
"Can you do me a favor?" the robber is seen saying. "Could you empty the till for me, please? Put it right here? … I really am sorry to have to do this, but I've got kids."
Henry asked, "How about I give you $40 dollars and this is it?"
"Well," the robber replied, "I can't do that, sir, I've got rent to pay, I've got bills"…."Thank you very much. I appreciate it and I really am sorry. And If I ever get back on my feet again sir, I'll bring it back."
He left with about $300, police say.
Urquhart did not immediately identify the man arrested Monday afternoon. The spokesman says the 65-year-old man arrested at a residence near the robbery site has convictions for armed robbery and forgery.
Jeff Glor has the story -- and the video -- on "The Early Show":