Police have arrested a 19-year-old man in the violent attack on a Jewish Orthodox activist who was beaten and robbed in front of his 5-year-old son in Brooklyn two weeks ago.
Officers collared Derrel Cooper, one of the four men seen on surveillance video pummeling Yosef Hershkop in Crown Heights on July 13, cops said Thursday.
Cooper faces three counts of robbery. The three other assailants are still at large.
Hershkop, 31, took to Twitter to confirm the arrest and thank the police and Jewish public safety volunteers “for their pursuit of justice and care.”
A day earlier, Hershkop complained that his young son “still has a lot of trauma” and is scared to walk outside in the wake of the incident.
According to law enforcement officials, Hershkop — a health care manager, lead poisoning safety advocate and married dad — was driving with his 5-year-old in the car along Montgomery Street when he was approached by four men as he attempted to park.

The men claimed that Hershkop had hit their car, and they demanded money.
Hershkop asked how much they wanted, and when the men did not answer, he threatened to call 911, police said.
One of the suspects proceeded to punch Hershkop in full view of his child — as seen in surveillance video released by the volunteer patrol organization Shomrim Crown Heights. The victim was left with cuts and bruises on his face.

Herhkop handed over $100 to his assailants, who then sped away in a white car.
GOP gubernatorial candidate Rep. Lee Zeldin weighed in on the incident on Twitter, writing: “Antisemitism in all forms must be unequivocally identified, called out & crushed.
“Too many in power look the other way regarding this violence rather than having the courage to turn our streets back over to law-abiding citizens. We must all stand with Yossy Hershkop & his family,” the pol wrote.