The complaint alleges that while incarcerated at Federal Correctional Institution Tucson, John Turscak, 52, stabbed Chauvin about 22 times "with an improvised knife," prosecutors said.

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

The investigation in the case was conducted by the FBI.

Attempted murder and assault with intent to commit murder violations each carry maximum penalties of 20 years incarceration, while assault with a dangerous weapon and assault resulting in serious bodily injury each carry maximum penalties of 10 years.

Chauvin was expected to survive following the attack last week in a prison in Arizona, the Minnesota Attorney General's office said earlier.

Chauvin is serving a 21-year federal sentence for violating Floyd's civil rights, as well as a concurrent 22-1/2 years for murder on his conviction in Minnesota state court.

Floyd's death in 2020 unleashed protests worldwide against police brutality and racism after Chauvin, who is white, knelt on the neck of the handcuffed Black man for more than eight minutes in a murder caught on cellphone video.

An attorney for Turscak was not listed in court records.

(Reporting by Kanishka Singh in Washington; Editing by Bill Berkrot)

By Kanishka Singh