Police said the robbery happened about 1 p.m. Monday at the Huntingdon Bank branch in the city's Carrick neighborhood.
The robber was speaking to someone on a cellphone during the heist, likely a getaway driver.
According to police, the robber stuffed the loot into a black purse. Police said a dye pack in the money exploded.
Witnesses said the man appeared to be somewhat soiled even before he entered the bank. Investigators said he was also wearing white athletic shoes, both of which were spattered with grease.