(CNN) -- Jim Nicholson could've just handed over the cash. Instead, he gave the would-be robber a run for his money -- and paid for it.
The 30-year-old bank teller said the suspect, dressed in black and wearing sunglasses, walked up to his counter at the Key Bank branch in suburban Seattle, Washington, demanding he fill the man's bag with cash.
"So I grab the bag ... I threw it on the floor," Nicholson told CNN Radio. He said he demanded the robber show him a weapon. When he realized there was none, Nicholson said, he lunged at the robber, chased him down the street, pinned him down and waited for the police.
That was Tuesday of last week. He lost his job Thursday.
"Policy violation," Nicholson said. "Basically, we are supposed to comply with any robber that would come in. We're supposed to just give him the money and let him go -- and obviously I did not do that."
Key Bank spokeswoman Anne Foster declined to comment on the incident, saying it's under investigation, and Nicholson's termination, saying it's a personnel matter.
"What I can say is Key's highest priority is to protect the safety of our employees and our clients," she said. "Our policies and procedures are in the best interest of public safety and they're consistent with industry standards."
"Money, after all, is insurable and it's replaceable," she added. "Lives are not."
Nicholson said he knew about the company's robbery policy before the incident, but said he acted on instinct. He found his dismissal a bit harsh, but said he doesn't plan to challenge it.
"I think that they probably wanted to set an example," he said. "I don't think they want other tellers to do the same thing."