Police in New York state said the man who robbed a Chase bank branch was armed with a pistol and dressed as "Star Wars" villain Darth Vader.
Lamb said the robber got into a "shoving match" with a customer who initially thought the costumed man was joking.
"The customer thought it might have been a joke, and not a serious attempt at a robbery," Lamb said.
Police said the intruder pulled out a gun and ordered the man to the floor.
Lamb said investigators were trying to determine how much money the holdup man was able to shove into a bag before fleeing.