Tensions between opposing protest groups outside the New York City mayor’s residence boiled over Saturday, when a protester hurled an improvised explosive onto the crosswalk, leaving protesters and police officers scrambling.

The device was capable of causing “serious injury or death,” the NYPD said Sunday, and multiple law enforcement sources told CNN two men arrested in connection with the device admitted to being inspired by ISIS. FBI New York’s Joint Terrorism Task Force, along with the US Attor ney’s Office for the Southern District of New York, is working with the NYPD on the investigation, the bureau said, noting the men remain in custody.

Police said both men are from Pennsylvania, The New York Times reported. CNN has reached out to the NYPD for further information.

The incident unfolded during the Islamic holy month of Ramadan outside the home of New York City’s first Muslim mayor, Zohran Mamdani, and his wife Rama Duwaji.

Mamdani and his wife were not home at the time, according to a source familiar with the situation.

An anti-Islam protest organized by right-wing influencer and pardoned January 6 rioter Jake Lang drew roughly 20 participants, while a counterprotest called “Drive the Nazis Out of New York” peaked at about 125 people, Commissioner Jessica S. Tisch said.

“The NYPD Bomb Squad has conducted a preliminary analysis of a device that was ignited and deployed at a protest yesterday and has determined that it is not a hoax device or a smoke bomb,” Tisch said in a post on X. “It is, in fact, an improvised explosive device that could have caused serious injury or death.”

Preliminary results show the device was made with TATP, an extraordinarily powerful and unstable explosive that’s easy to obtain, multiple law enforcement officials told CNN.

Analysis of a second device recovered at the scene is ongoing. No injuries were reported.

Both devices were constructed with what is suspected to be homemade explosive material and fragmentation in the form of nuts, bolts and screws, law enforcement sources said.

Sunday, the NYPD said it was investigating a suspicious device in a vehicle just a few blocks south of the mayor’s home, Gracie Mansion, “in connection with” Saturday’s incident, police said in an X post.

The area was frozen to traffic and pedestrians late Sunday afternoon while authorities conducted “limited evacuations” of buildings and while the bomb squad checked out and removed the device, police said.

The suspicious device was eventually removed from the area for further testing, and evacuees were allowed to return to their homes, NYPD said in an update.

The two groups were separated into designated protest areas by NYPD officers, but tensions escalated shortly before noon. At around 12:15 p.m., a protester associated with Lang’s group used pepper spray against counterprotesters, Tisch said.

About 20 minutes later, an 18-year-old counterprotester “lit and threw an ignited device toward the protest area,” which landed on a crosswalk, Tisch said.

“Witnesses reported seeing flames and smoke as it traveled through the air before it struck a barrier and extinguished itself a few feet from police officers,” she added.

Video captured by the Citizen app shows the moment the device was thrown, with protesters and police officers scrambling to get away from where it landed. From another angle, a man is seen leaping over someone speaking on a megaphone and throwing the ignited device.

The man then ran southbound to retrieve a second device from a 19-year-old man before lighting it and starting to run, Tisch said. He dropped the second device on a street, and officers secured the area, taking both men into custody.

The video shows smoke in the air and more people running from the second device as police detain a man on the ground.

The NYPD bomb squad examined both devices, preliminarily determining they were slightly smaller than a football and appeared to be a jar wrapped in black tape containing bolts, screws and a hobby fuse, Tisch said.

In total, six people were arrested: the two responsible for the devices, the person who deployed pepper spray and three others for disorderly conduct and obstructing traffic, Tisch said.

Mamdani on Sunday called the Lang-organized protest “rooted in bigotry and racism,” saying, “Such hate has no place in New York City.” But he said what followed was “even more disturbing.”

“Violence at a protest is never acceptable. The attempt to use an explosive device and hurt others is not only criminal, it is reprehensible and the antithesis of who we are,” the mayor said.

The mayor and his wife are safe, and Mamdani has been in contact with Tisch, said press secretary Joe Calvello.

The mayor thanked the men and women of the NYPD for their bravery and quick action.

Officers established a safety perimeter and began canine sweeps and manual canvassing of surrounding blocks to search for additional hazards, which is still ongoing, Tisch said.

She said there is no indication the incident is related to the ongoing conflict in Iran but stressed the investigation remains active “given the heightened threat environment.”

Tisch commended officers for running toward the man carrying the ignited device, “putting the safety of others in their sworn duty to protect and serve above their own personal safety.”

New York Gov. Kathy Hochul said she had been briefed and was “grateful there are no reported injuries.”

“New York respects the right to peaceful protest, but we have zero tolerance for hate or violence,” Hochul said. (CNN)