A mob of up to 20 anti-ICE protesters swarmed and attacked immigration agents outside a San Francisco courthouse on Wednesday, with one keffiyeh-clad agitator allegedly armed with a knife threatening to stab an officer and go after his family, officials said.Adrian Guerrero, a U.S. citizen, slashed the tire of a government vehicle during the clash at the immigration courthouse on 100 Montgomery Street, according to the Department of Homeland Security (DHS).The incident unfolded as ICE agents carried out a removal operation, when protesters surrounded them and physically assaulted four officers, throwing punches and deploying pepper spray.WATCH: ICE AGENTS FIGHT OFF MASKED MOB OUTSIDE BLUE CITY IMMIGRATION COURTStanding within arms length, Guerrero made repeated threats, saying, "Im going to f--- you up," "Im going to go after your family," and "Im going to stab you," according to DHS, citing court filings.At the time of his arrest, the suspect had a knife, orange-tinted goggles and a patterned keffiyeh, a scarf often associated with pro-Palestinian activism.Agents sustained injuries from pepper spray and one officer suffered a jammed finger.Guerrero has been charged with assault on a federal officer and destruction of government property, according to DHS.ICE DISPELS RUMORS ABOUT VIRAL VIDEO SHOWING AGENTS SMASHING WINDOW TO ARREST ILLEGALU.S. Federal Protective Services and San Francisco police responded and helped clear the area, DHS said.DHS Secretary Kristi Noem said ICE agents are facing a 1,000% increase in assaults, calling them "the worst of the worst criminal illegal aliens.""These acts of violence are fueled by sanctuary politicians rhetoric vilifying our law enforcement," Noem said."We will not let this violence stop us or slow us down. Every day, our law enforcement continues to enforce the law and arrest the most depraved criminals, including pedophiles, terrorists, murderers, gang members, and sexual predators."CLICK HERE TO GET THE FOX NEWS APPThe Montgomery Street courthouse has been the site of multiple violent clashes between protesters and ICE agents. Last month, video surfaced of similar scuffles outside the court.Protesters have long opposed ICEs practice of detaining individuals at courthouses, criticizing the use of plainclothes officers and unmarked vehicles as tactics that they claim spread fear and reduce accountability.The attack came weeks after violent riots in Los Angeles, where ICE agents were assaulted during courthouse protests part of what DHS says is a sharp nationwide rise in attacks on its officers.