Who sucker-punched man in dispute over dog?

NEW YORK- A man was critically injured during a dispute over a dog in Midtown Manhattan on Tuesday evening, reports the New York Post.

The man was walking his dog and was with a friend when he was punched in the face by another man. He was rushed to New York Presbyterian Hospital, where he is now in critical condition, cops say.

The man had been arguing with the suspect for stepping over the pooch while walking on the sidewalk. That argument ended with the dog-walker falling to the ground, hitting his head, according to the Post.

Police are still searching for the suspect, who they say is in his 30's, 5-foot-10, and 170 pounds. He has blonde hair.

A witness posted a video of the attack to YouTube.