A federal inmate is accused of stabbing fellow inmate and former Minneapolis police officer Derek Chauvin 22 times after thinking about and planning the attack for a month, federal prosecutors said.

John Turscak, 52, attacked Chauvin, who is in prison for the murder of George Floyd, with an “improvised knife” last week at Federal Correctional Institution, Tucson, the U.S. Attorney’s office said Friday.

He told federal prosecutors he had been thinking about assaulting Chauvin for about a month because Chauvin was such a high-profile inmate.

Turscak has been charged with attempted murder, assault with intent to commit murder, assault with a dangerous weapon and assault resulting in serious bodily injury, according to federal prosecutors.

Chauvin was seriously injured in the Nov. 24 attack, a law enforcement source told NBC News at the time.

Turscak told federal prosecutors he chose that day, the day after Thanksgiving commonly known as “Black Friday,” to symbolize the Black Lives Matter movement and the “Black Hand” symbol of the Mexican Mafia.

Floyd’s death sparked protests across the nation and world and forced a national reckoning of police brutality and racism.

Turscak told federal prosecutors that he would have killed Chauvin had they not responded to the attack so quickly, according to the USDA’s criminal complaint.

“Responding employees initiated life-saving measures for one incarcerated individual,” the source said.

Chauvin is serving a 22 1/2-year sentence for kneeling on Floyd’s neck for 9½ minutes while Floyd said he couldn’t breathe and went limp. The former officer is simultaneously serving a 21-year federal sentence for violating Floyd’s civil rights and a 22½-year state sentence for second-degree murder.