(AP) — A federal inmate was charged Friday with attempted murder in the prison stabbing of Derek Chauvin, the former Minneapolis police officer convicted of murdering George Floyd.

John Turscak stabbed Chauvin 22 times in the law library at the Federal Correctional Institution in Tucson, Arizona, with an improvised knife, federal prosecutors said. Turscak, 52, told correctional officers he would’ve killed Chauvin had they not responded so quickly, prosecutors said.

Turscak later told FBI agents that he’d been thinking about assaulting Chauvin for about a month because he is a high-profile inmate but denied wanting to kill him, prosecutors said.

Turscak told the agents that he attacked Chauvin on Black Friday, the day after Thanksgiving, as a symbolic connection to the Black Lives Matter movement and the “Black Hand” symbol associated with the Mexican Mafia gang, prosecutors said.

An attorney for Turscak was not listed in court records and Turscak, who has represented himself in numerous court matters from prison, remained in custody on Friday.

Chauvin, 47, was sent to FCI Tucson from a maximum-security Minnesota state prison in August 2022 to simultaneously serve a 21-year federal sentence for violating Floyd’s civil rights and a 22½-year state sentence for second-degree murder.

Chauvin’s lawyer, Eric Nelson, had advocated for keeping him out of general population and away from other inmates, anticipating he’d be a target. In Minnesota, Chauvin was mainly kept in solitary confinement “largely for his own protection,” Nelson wrote in court papers last year.

Floyd, who was Black, died on May 25, 2020, after Chauvin, who is white, pressed a knee on his neck for 9½ minutes on the street outside a convenience store where Floyd was suspected of trying to pass a counterfeit $20 bill.

Bystander video captured Floyd’s fading cries of “I can’t breathe.” His death touched off protests worldwide, some of which turned violent, and forced a national reckoning with police brutality and racism.