Donning a yellow construction helmet, a man walked into a Prince Street bank, flashed a gun, demanded money and then fled on a mountain bike Tuesday. 
    
Alexandria police say the suspect, a 6-foot-1-inch black man with a thin build and roughly 30 to 40 years old, entered the Virginia Commerce Bank at 1414 Prince St., about 12:28 p.m. He approached a teller, pulled out a handgun and demanded cash, according to authorities.
    
Money in hand, the robber left the scene riding on a silver mountain bike, authorities said. No one was injured in the holdup.
    
Police arent releasing how much money was taken in the heist.
    
Along with the construction helmet, the man wore blue jeans and a black sleeveless shirt over a white long sleeve shirt, according to authorities. 
    
Police urge anyone with information about the robbery to contact the department at 703-838-4444 or the Crime Solvers tip line at 703-838-4858. Witnesses can remain anonymous, police said.