BROOKLYN - Police are investigating after a passenger made a bomb threat on the L train. 

It happened on Sept. 17 around 5:45 p.m. aboard a northbound L train that left the Bedford Avenue station.

According to police, the passenger yelled " bomb" then counted down from five and yelled out "boom." 

A passenger took a picture of the suspect with her cellphone before she left the train at the 1st Avenue station, police say.

He is described as being between 30 and 40 years old, 5'10'' tall and was last seen wearing a white T-shirt and blue pants. 

Anyone with information is asked to call Crime Stoppers at 1-800-577-TIPS.