"As the teller is giving her money, complying with the demands of the suspect, she's trying to keep the note, so he takes out a [small-caliber hand] gun and takes the note from her," he said.
The suspect then allegedly put the money in a colored bag, walked out of the bank and into a two-tone gold Saturn, and was last seen traveling south on Brand Boulevard, Balian said.
No one was injured in the robbery, and police did not know Thursday evening how much money was taken.
The bank was closed the remainder of Thursday afternoon as authorities investigated.
The suspect is described as being in his 20s, 5-foot-5-inches tall with a heavy built and a mustache, wearing a gray shirt and dark-colored jacket, a beanie with an unknown logo on it and dark-colored pants, Balian said.
Anyone with any information should call Det. Keith Soboleski at (818) 548-3987, or call the anonymous Glendale Crime Stoppers line at (818) 507-STOP.