A gunman fired through the door of an occupied Brooklyn apartment this week, new video released by cops shows. 

The footage shows three men walking into an apartment building at South Third and Havemeyer streets in Williamsburg around 12:20 a.m. Monday.

Then it cuts to one man approaching a fourth-floor apartment door alone and knocking a few times before pulling out a gun and firing a single round directly at the door. 

The bullet flew into the apartment and struck the upper part of a couch. 

Two men, ages 23 and 18, were inside, but they were not struck, police said. 

It’s unclear whether the men, or the apartment, was specifically targeted. 

The trio took off after the shooting, and cops were still looking for them Tuesday.