A 21-year-old man was shot in the head and killed in a broad daylight “execution-style” murder at a Brooklyn auto repair shop on Tuesday, according to authorities and witnesses.

The victim was gunned down at close range by an assailant he appeared to recognize at the Robel Auto Repair shop on Meserole Street in Williamsburg at around 2:15 p.m., the NYPD and witnesses said.

The cold-blooded killing was captured on a neighboring business’s surveillance camera and local resident Iris Gomez viewed the shocking footage.

The victim was sitting in the passenger seat of a car outside the auto shop when the shooter circled the block on a scooter before coming back and parking across the street, according to the video.

The suspect then walked across the street and the victim appeared to catch a glimpse of his eventual killer, Gomez said.

“It looked like in the camera you could see [the victim] like scoot down, like he saw someone like that he didn’t want to see apparently,” she said.

After the masked man walked by, the victim was then seen getting out of the car, apparently thinking he was in the clear – but was immediately shot in the back of the head by the masked assailant as he emerged.

“He just caught him execution style,” Gomez explained.

“As soon as the bus came, and the bus took off, that’s when [the assailant] saw the guy come out of the car and he shot him right in his head,” she said.

Other witnesses say they saw first responders performing chest compressions on the victim, but to no avail.

The unnamed victim was taken in critical condition to Elmhurst Hospital, where he was declared dead, cops said.

The shooter was wearing all black, including a facemask, and fled down Meserole Street on an electric scooter, the NYPD said.

A motive behind the murder wasn’t immediately known.

No arrests have been made. The NYPD says an investigation is ongoing.