It happened around 11:50 a.m. Wednesday, Dec. 29 in Commack.
That's when the man entered Capital One, located at 2050 Jericho Turnpike, and handed a teller a note threatening violence and demanding money, Suffolk County Police said.
The teller gave the man cash from the drawer and the man fled on foot.
The man was wearing a mask, a hooded sweatshirt with the hood up, a ski cap and gloves.
Detectives are asking anyone with information to call the Suffolk County PD Major Case Unit at 631-852-6553 or anonymously to Crime Stoppers at 1-800-220-TIPS. All calls will be kept confidential.
Check back to Daily Voice for updates.
Click here to follow Daily Voice Brentwood and receive free news updates.