amphotora/iStockBy MIKE LEVINE and JOSH MARGOLIN, ABC News

(WASHINGTON) -- Federal authorities are increasingly worried that “violent opportunists” are infiltrating otherwise peaceful protests across the country and could be “emboldened” to attack law enforcement as they see police officers targeted elsewhere, according to new warnings from the FBI and Department of Homeland Security.

In fact, the FBI’s field office in Boston “received credible intelligence that rioters are looking for officers’ home addresses via public [records]," the FBI office said in an internal report issued Tuesday.

Protests throughout the nation are calling for major police reforms and seeking justice for George Floyd, the unarmed black man who died while being arrested early last week by a Minneapolis police officer, who has since been charged with murder. Violence has erupted during many of the protests over the past week, with nearly 10,000 people arrested in recent days.

DHS on Tuesday distributed a private “intelligence note” to the nation’s local, state and federal law enforcement agencies, warning “that some violent opportunists have become more emboldened following a series of attacks against law enforcement during the last 24 hours nationwide.”

“This could lead to an increase in potentially lethal engagements with law enforcement officials as violent opportunists increasingly infiltrate ongoing protest activity,” declared the DHS report, noting that “several incidents” in recent days involved “violent opportunists” not only targeting police but “shooting into crowds of protestors.”

In the document, DHS reported that on Tuesday, at least one “violent opportunist“ drove into a crowd of protesters in Asheville, North Carolina, firing “several shots into the crowd before speeding away.”

“There were no reported injuries and we lack information suggesting that this was a preplanned or coordinated incident,” DHS added.

In Davenport, Iowa, after a protester there was shot and killed Monday, a law enforcement vehicle on patrol was shot 13 times, injuring an officer in the vehicle, DHS said, citing media reports.

In Las Vegas on Monday, a police officer was killed as officers tried to arrest several people who were allegedly "throwing bottles and rocks at officers.” A witness told local news media that “as one officer was struggling with a protestor, another person walked up and shot the officer in the back of the head,” DHS wrote in its intelligence note.

Also in Las Vegas on Monday, police encountered a man who was carrying multiple firearms and “appeared to be wearing body armor” -- when “the subject reached for a firearm,” an officer fatally shot him, according to DHS.

Law enforcement reports issued in recent days depict police officers being targeted with bricks, fireworks, Molotov cocktails and gunfire in cities such as New York, St. Louis, Philadelphia, and Los Angeles.

On Tuesday, a retired St. Louis police captain who became a small-town police chief was found fatally shot outside a pawn shop that was looted.

And in the midst of protests in Oakland, California, on Friday, a gunman opened fire on two officers from the Federal Protective Service, who were reportedly protecting a courthouse. One of the officers was killed; the other was critically wounded.

“The perpetrators committed these senseless acts of violence while hiding behind those expressing their First Amendment right to lawfully protest,” the assistant director for infrastructure protection at DHS, Brian Harrell, said Monday during an online summit hosted by the Security Industry Association.

“As Americans, we should all support peaceful demonstrations and exercising our constitutional rights. However, violence, destruction, and bloodshed in the streets is never the answer,” he added.

In their reports, neither DHS nor the FBI field office offered details about the “violent opportunists” they are tracking.

President Donald Trump and Attorney General Bill Barr, however, have publicly pointed to the radical left-wing antifa group as driving much of the violence over the past week. Earlier DHS documents, meanwhile, have warned that certain right-wing radicals are seeking to incite violence with postings online.

Copyright © 2020, ABC Audio. All rights reserved.