When Kevin Alfaro noticed a masked police officer befriending a counterprotester who had threatened him at a Black Lives Matter demonstration in Nutley, N.J., on June 19, he whipped out his phone and took a picture.

Then he tweeted: “If anyone knows who this b---- is throw his info under this tweet.”

Now, Alfaro and four others who retweeted the post have been charged with cyber harassment, a fourth-degree felony that carries up to 18 months of incarceration and a $10,000 fine.

A complaint sent July 20 to Georgana Sziszak, who retweeted the post, first reported by the Verge and reviewed by The Washington Post, claims that the tweet caused the officer to “fear that harm will come to himself, family and property.”

The Nutley Police Department did not immediately respond to a message late on Thursday.

Alan Peyrouton, Sziszak’s lawyer, said he was bewildered by the charge.

“I’ve never seen anything like it,” he told The Washington Post. “How could this rise to the level of a crime? She just mindlessly retweeted.”

Social media has played a key role in the resurgent Black Lives Matter movement, as activists have spread their message and chronicled protests. But police have also used those images, as in Philadelphia this week where Facebook posts and a student’s photographs led to charges against six people accused of setting a police car on fire. Prosecutors have also gone after activists for sharing police information. In Iowa, two protesters were charged in July with a felony for allegedly flashing on TV a bulletin snatched from an officer’s pocket that had suspect information.

But Alfaro, 21, Sziszak, 20, and the three others who shared his tweet were simply expressing their First Amendment rights, Peyrouton argued.

“You’re allowed to express your disapproval or dissent of how your government is behaving,” he said. “It is protected speech.”

Alfaro wrote on a GoFundMe page that he was at a peaceful Black Lives Matter protest on June 29 when a group of counterprotesters became physically threatening. He then saw a Nutley police officer, later identified as Detective Peter Sandomenico in Sziszak’s summons, acting friendly with the counterprotesters. Sandomenico had covered up his badge number and was wearing a “Blue Lives Matter” mask, Alfaro added.

“As a citizen exercising my First Amendment rights, I felt threatened that a public servant was befriending blatant racists,” Alfaro said.

Alfaro sent his tweet, which has since been deleted, to his 900-plus followers. But it got hardly any traction, based on an archive of the tweet, besides a handful of likes and five retweets. The police summons sent to Sziszak does not note whether the tweet in fact led to the officer’s information being made public.

Sziszak, a pharmacy technician, wasn’t at the protests. On her GoFundMe page she writes that she retweeted it in support of her friend.

“I did not reply, did not say anything against this cop, and had zero clue to who he was,” she said. “I simply retweeted because I feel that just as with anyone we should hold our officers accountable."

Now Sziszak worries that the retweet could derail her life.

“I am now at risk of giving up my career, serving time, and having a record,” she wrote. “Im upset that an officer claims he feels threatened & cyber bullied over me RETWEETING a tweet asking for his information. I feel that he is taking advantage of him being a cop and is putting me in a place of fear for his advantage.”

Peyrouton, Sziszak’s lawyer, said he suspects that prosecutors are going after the five co-defendants because they are concerned about police officers being doxed online.

But without having seen any of the evidence from prosecutors, he said he remains perplexed over the felony charge.

“It’s a huge question mark,” he said.