Cellphone video caught the moment when a bat-wielding man beat a bicyclist unconscious on a Brooklyn street corner — and except for one person who stepped in to prevent further injury, every other bystander simply watched or just walked on by like nothing was happening.

Here's the clip:

What are the details?

Police told WINS-AM the 54-year-old victim was riding his bike in the vicinity of Flatbush and Parkside Avenues around 5:30 p.m. Wednesday when the unprovoked attack occurred.

One man stepped in to stop the attack, although the assailant tried a few more times to get swings in without success.

Image source: Twitter video screenshot via @NY_Scoop

Soon NYPD officers spotted a crowd, walked over, and witnesses identified a suspect who was was standing nearby, the New York Daily News said, adding that he was taken into custody.

Ashanti Robinson, 46, is facing charges of assault, menacing, and criminal possession of a weapon, WINS said.

Officials said the victim and suspect are strangers and that the attack was random, the station added. There have been a number of unprovoked attacks in New York City of late.

The victim was taken to Kings County Hospital in critical but stable condition with cuts and swelling to the head, authorities told the New York Post. The victim was still unconscious Thursday and has not been interviewed by police, officials told the Daily News.

What do we know about the suspect?

The Post, citing sources, said Robinson has 14 prior arrests that are sealed — and one unsealed arrest in 2014 for criminal possession of a weapon.

In May 2014, Robinson was arrested after police said he had two 15-inch swords hanging from his belt while walking down Flatbush Avenue near Martense Street, WABC-TV reported, adding that the arrest took place less than a mile from the bat attack.

What was the reaction to the bat attack?

A number of Twitter commenters were angered not only by the attack itself but also because just about every bystander did nothing about it:

• "Meanwhile people are just walking by or recording with their phones. Brooklyn strong, my a**," one user said. "This is why you don't give up your guns."
• "How the F can people just walk by this and do nothing!?" another commenter wondered. "There were some big guys there, too."
• "What kind of person stands around and does nothing or films this?" another user asked. "Unless this guy raped/murdered this other persons friend/family, in which case I'll happily apologize. Good to see at least one decent human in the vid."

One user offered the following observation: "This is absolutely why NYers need to be able to carry. If the biker had a gun, after that first swing, I would be unloading on his a**."

Another commenter added this quip: "What is needed are more social workers."