An active-duty U.S. Air Force sergeant charged in the fatal shooting last week of a Santa Cruz County, California, deputy sheriff and critically injuring another has been linked to the militant right-wing Boogaloo movement .

Steven Carrillo, 32, is also a suspect in the fatal shooting last month of Federal Protective Services officer Dave Patrick, who was patrolling a federal building during nearby anti-racism protests in Oakland, a law enforcement source told the San Jose Mercury News.

Carrillo allegedly scrawled the letters boog, for Boogaloo, in blood on the hood of a car along with a phrase linked to the group as he fled police last Saturday, NBC News reported. Boogaloo is code for a violent insurrection by the right-wing followers.

The phrase written on the car, I became unreasonable, is part of a call to arms by members of the group who appear on social media sites armed and urging followers to become unreasonable. Its not clear whose blood was used; Carrillo was shot by police before his capture.

A former friend told the Mercury News that Carrillo was sharing memes of the Boogaloo movement in his Facebook comments.

Carrillo was charged Thursday with 19 felonies, including murder in the death of Sgt. Damon Gutzwiller , attempted murder involving four law enforcement officers and a local resident, along with explosives charges and carjacking charges after the rampage in Ben Lomond, California, where Carrillo lived with his father.

Gutzwiller and Deputy Alex Spencer were allegedly ambushed by Carrillo as they responded to a call from a concerned resident, according to the complaint. Carrillo lobbed pipe bombs at other officers responding and hijacked a car in a bid to escape, according to court documents.

News of the violent attack on law enforcement comes as President Donald Trump and Attorney General William Barr have repeatedly accused left-wing anarchists and members of antifa of fomenting violence in largely peaceful anti-racism protests across the nation in the wake of the brutal police killing of George Floyd in Minneapolis. Arrest records reveal scant evidence backing that claim .

Last week, however, three men linked to the Boogaloo movement were arrested and charged with state and federal conspiracy violations for allegedly plotting to trigger violence at anti-racism protests in Las Vegas . They were also accused of possessing Molotov cocktails.

One of the last messages attributed to Carrillo on Facebook, which has since been removed, was a post on a group gun site of the video of police in Buffalo, New York, shoving a 75-year-old man to the ground, where he appeared to be knocked unconscious and was bleeding from his ear, according to NBC. Trump tweeted Tuesday that he suspected the injured peace activist, Martin Gugino , still recovering in a hospital with a brain injury, was part of some kind of left-wing conspiracy and not a victim of police violence.

Online Boogaloo messaging has grown increasingly extreme in the wake of pandemic lockdowns and protests over Floyds death, according to a report by the independent nonprofit organization Network Contagion Research Institute.

Elements of The Boogaloo have evolved from a gathering of militia enthusiasts and Second Amendment advocates into a full-fledged violent extremist group, which inspires lone wolf actors and cell-like actors alike, institute Director Joel Finkelstein told NBC News. He said researchers believe more attacks on law enforcement are almost inevitable.

The phrase Carrillo reportedly wrote on the car, I became unreasonable, is a reference to a quote by Marvin Heemeyer, an anti-government extremist who bulldozed 13 buildings in Granby, Colorado, in a zoning dispute in 2004. Heemeyer known as Killdozer by members of the Boogaloo movement killed himself after the rampage, almost 16 years to the day of Carrillos alleged attack.

Carrillos attorney Jeffrey Stotter has not discussed the case but told reporters outside court Friday that Carrillo suffers from a traumatic brain injury and extreme personal family loss, which he did not detail.

Im simply pointing out there are more colors to Mr. Carrillo and what his possible motivation and what his involvement is beyond what you might hear and see from the complaint, he added.