The California man who allegedly gunned down a sheriff’s deputy and critically injured another in an ambush scrawled a shorthand in blood for the “Boogaloo” far-right extremist movement before he was caught, according to a report.

Steven Carrillo, 32, a US Air Force sergeant, was stationed at Travis Air Force Base when he allegedly killed Santa Cruz County Sheriff’s Sgt. Damon Gutzwiller on June 6 during a pursuit after reports about a suspicious van laden with guns and bomb-making devices.

Before he was arrested, Carrillo wrote “boog” and “I became unreasonable” in blood on the hood of a vehicle, according to NBC News.

The anti-government movement, which began on the extremist site 4chan, seeks to start a second American civil war. Three members of the fringe group who wanted to incite a riot in Las Vegas in an alleged attempt to overthrow the US government have recently been arrested.

The phrase “I became unreasonable” has emerged as a meme in public Boogaloo communities in social media, including on Facebook, where a man was seen holding a Boogaloo flag during a protest along with the words “become unreasonable,” NBC News reported.

The phrase refers to a quote written by anti-government extremist Marvin Heemeyer, who bulldozed 13 buildings in Granby, Colorado, on June 4, 2004, in retaliation for a zoning dispute, according to the network. He killed himself after the rampage.

Carrillo also wrote “Stop the duopoly” — a political slogan used by third-party and libertarian candidates — in blood on the vehicle, NBC News reported.

On Facebook, Carillo’s profile image showed George Washington and other US presidents brandishing weapons and tactical gear, as he expressed anti-police views and espoused pro-gun causes.

In one of his last posts, Carrillo shared the infamous footage of Buffalo police shoving a 75-year-old man to the ground in a group called “A Gun Page for Poors Who Know They Are Poors,” NBC News reported.

Facebook has since removed his page and posts.