PHOENIX (AP) -- Federal authorities said Friday that they're searching for a man who robbed one bank in the Phoenix metropolitan area and tried to rob two others using fake bombs.
Phoenix FBI officials said the so-called "Dynomite" bandit was at a Chase Bank in Peoria on July 3, a Wells Fargo Bank in Anthem on Dec. 21, and another Chase branch in Scottsdale on Wednesday.
In each case, the man gained entry to the bank after normal business hours through a hole cut in the roof, authorities said. He then placed a device that looked like an explosive inside the bank and exited undetected.
The following morning when the bank opened, the suspect made a phone call demanding money and threatened to blow up the bank if his demands weren't met.
The FBI said the man got money in only one robbery, an undisclosed amount from the Peoria bank.
Authorities are offering a $15,000 reward for information leading to his arrest and conviction.
FBI officials said they gave the man the misspelled "Dynomite" nickname because the explosive devices he used were fake. All serial robbers are given a moniker so they stand out with the public, the officials said at a news conference.
"The devices in all three are very realistic, so much so that employees think it's an explosive bomb," said Mark Hoffman, FBI supervisory special agent. "The devices were all inert. There were no explosive parts."
Employees from the Anthem bank evacuated the building instead of listening to the robber's demands, Hoffman said.
In the Scottsdale incident, employees preparing for business found the fake bomb taped to the underside of an ATM in the bank's vestibule, the FBI said.
Hoffman said it's believed the suspect spent a week or more conducting extensive surveillance of each bank, locating exits and studying when employees arrive and leave.
He added the man may have a military or law-enforcement background.