Williamsburg resident and repeat sex offender Joseph Grunwald, 31, was arrested on Wednesday on charges of sexually assaulting a 14-year-old boy in Monsey. 

According to the charges, Grunwald told the victim that he had access to mikvahs, to which he would lure boys and assault them. He also told the boy he drove a school bus, to show he was entrusted with minors.

Grunwald, who has previously pleaded guilty to two crimes against children, has groomed, sexually assaulted, blackmailed, and threatened the victim in recent months, according to court documents filed by the office of Breon Peace, the U.S. attorney for the Eastern District of New York, which is part of the U.S. Department of Justice. Federal investigators believe that Grunwald has been doing the same thing to other boys as well, despite his prior crimes. 

Grunwald first contacted the boy around April using Telegram, a popular online instant messaging service that uses end-to-end encryption, a private communication system that makes it a platform of choice for many harmful actors. Grunwald then began asking the boy sexual questions and eventually enticed the boy to send him a picture of his private parts. Grunwald later shared this picture with others. The man groomed the boy for sexual assault by saying he would help the boy by getting him a cell phone, which he expected the boy to pay for through sexual activity and money.

Grunwald used the offer of the cell phone to sexually assault the child and harass him “relentlessly,” according to the complaint. When the two met in person in Monsey for Grunwald to give the boy the phone, Grunwald “placed his hand inside [the boy’s] pants” and fondled the victim’s genital area for several minutes, the federal law enforcement officials said.

Grunwald also demanded money from the victim and threatened to hurt him if he didn’t pay. 

“If you don’t give me the money, I’m going to knock on your mother’s door,” Grunwald said in Yiddish. “If you don’t talk to me with respect, I’m going to be on top of you your whole life.”

The man made many other threats against the boy, and was still doing so as of last month. 

“You blocked me, and you lit a fire under me. I’m going to beat you,” Grunwald wrote. He threatened to tell the boy’s 12-year-old brother “everything,” and at one point, he even seemed to threaten to kill the 14-year-old, writing, “I am warning you with your life.” 

In other messages Grunwald sent to the boy, the man boasted about harming other boys, and referred to harassing boys as “helping” them. “I do it with teenagers every day,” he said. “I don’t need you. I have other boys that I help, and I’m no longer going to help you.”

Grunwald also said that he “takes boys who owe him a debt to the mikvah (a Jewish ritual bath) so that they can repay their debt by allowing him to see them naked.” To prove that he had access, he sent the boy photos of mikvahs and what appeared to be dormitory rooms.

According to the DOJ, Grunwald lives across the street from an elementary school.

Grunwald apparently attempted to avoid arrest on Wednesday, according to the DOJ. Agents from the Federal Bureau of Investigation first came to Grunwald’s Williamsburg home, but did not find him there. “A back door from his bedroom to the outside was left unlocked, consistent with a person leaving from the bedroom in haste,” the DOJ said.

They later found Grunwald in Borough Park, where he continued to try to evade arrest. “He was inside a building and repeatedly thrust his head out of an exterior door, scanned the area and returned inside,” the DOJ said. “Eventually he emerged and began to walk away rapidly, at which point he was arrested.”

Grunwald’s criminal history may cause the court to penalize him more harshly than it would otherwise, the DOJ said. In 2018, he pleaded guilty to sexual abuse of a child under 11, and to sexual abuse of a child under 14. He is currently serving probation supervised by the New York City Department of Probation. 

The DOJ is seeking to ensure that Grunwald does not get released on bail, as they believe doing so would be too risky, as he could potentially harm others in the community and is also a flight risk.

“The government submits that no condition or combination of conditions would reasonably assure the safety of [the boy] and the community, or ensure the appearance of the defendant in court,” a letter to the federal court says. “He also has a strong incentive to flee in light of the strong evidence against him, the 20-year mandatory minimum sentence he faces, and the possibility of additional charges.”