Some witnesses believe he's an old man, but authorities say it's highly possible that the "Geezer Bandit" is actually a younger man wearing a mask. His crime spree is attracting a lot of attention.
He's held up 13 banks over the last 18 months, most of them in the San Diego area.
But two weeks ago the Geezer Bandit walked into a Bank of America in the city of Goleta, northwest of Los Angeles. He pointed a gun at a teller and demanded money before making his getaway.
Witnesses have described him as a white male, between 60 and 70 years old. But authorities say his elderly appearance may be deceiving.
"There are many witnesses that have described a mask. In the most recent robbery we have witnesses that say it appeared that he was speaking through a mask, that his lips were barely moving," said FBI Spokeswoman Laura Eimiller. "His lips were hardly moving."
Thousands of people have become fascinated by the Geezer Bandit. There are Facebook pages set up in his honor. Many of the postings praise him for his crimes and encourage him to run.
"I'm not that partial to bank robbers. My money's in a bank. I don't think it's really a folk hero here," said Nashville resident Lynn Bush.
"It's ridiculous. Why are you condoning such a ridiculous thing? It's not OK what he's doing, why are you making him a hero?" said New York City resident Julia Handel.
The FBI says the bandit should be taken seriously because he is using a weapon and threatening to shoot. But authorities say all the publicity could be useful.
"It's good because it may help us catch this person, but certainly it's nothing to be taken lightly," said Eimiller.
Some say the people rooting for the robber on social networking sites aren't thinking clearly.
"If you're praising someone, you have to also imagine what if you were victimized? " said West Hollywood resident William Malpede.
"If you're praising a bank robber on Facebook, you really have too much time on your hands," said Nashville resident Sam Bush.
The FBI and some of the banks are offering a $20,000 reward for information leading to an arrest and conviction.
If you think you have information that will help authorities find the Geezer Bandit, you can call San Diego County Crime Stoppers at (888) 580-8477.