Disturbing video released by police Wednesday shows the moment a man randomly attacks a 70-year-old stranger in Brooklyn.

The incident took place around 5:15 p.m. Thursday in front of 148 Parkside Ave. in Prospect Park South when the man randomly slugged the victim in the back of the head –– causing her to collapse to the ground, according to surveillance video and police.

The suspect then casually walks away eastbound on Parkside Avenue, video shows.

The woman refused medical attention when EMS arrived.

There was no interaction between the two before the attack, police said.