KOMO/ABC News

A Washington state good Samaritan who sells Christmas trees for charity was left dumbfounded when a woman who did not work on his lot began selling his trees, then once caught absconded with the cash she'd made.

Justin Mayfield, 30, has opened Two-Five Trees in Tacoma every holiday season for the past three years to support the nonprofit organization he founded called Locallife, which works to promote neighborhood improvement across Tacoma.

Mayfield was surprised to learn last week that the lot of trees, which is left unattended for a part of the day so that it can be well-staffed when sales are prime, was invaded by a woman from about 1 p.m. to 3 p.m., who began to sell trees to customers for $20 apiece.

"The lady went and walked down there, and was watching, and then started selling trees. She didn't even bother to take down the signs!" Mayfield told ABCNews.com. "She was selling $80 Nobles for $20."

Mayfield said that the woman, who has not been apprehended by police, even helped the people she sold the trees to load them into their cars. She was spotted when the afternoon staff arrived to work.

"Mayfield told ABCNews.com that his staff members saw the perpetrator loading a tree into a car, and asked her where she got it. The woman told them that it was "some other lady."

"[The perpetrator] walked with our guys back into the lot and said, 'I guess she's gone.' Then another customer said, It's her, she's the lady selling the trees.' Then the woman said, 'Good luck proving it.' Then she ran."

The perpetrator, who Mayfield said was an African-American woman who looked to be in her 30s, was followed by the staff to the other side of the neighborhood, but they couldn't catch her.

In the end, the woman sold about $500 worth of trees, for a profit of about $180. Though Mayfield has filed a police report, he said she eluded the lot's security cameras.

"She was in a blind spot somehow," he said. "I think we got a coattail."

The tree sale site has now resumed hours in the morning, so there's no gap between the morning and afternoon shifts. It has also moved its security trailerfrom across the street into the middle of the lot.