An inmate has been charged with attempted murder for stabbing Derek Chauvin 22 times last week at a federal prison in Tucson, Ariz., the U.S. Attorney’s Office in Arizona said on Friday.

The inmate, John Turscak, 52, is accused of stabbing Mr. Chauvin with an improvised knife on Nov. 24.

Mr. Turscak told investigators that he had been thinking about assaulting Mr. Chauvin for about a month because Mr. Chauvin, who is serving more than 20 years in prison for murdering George Floyd, is a high-profile inmate, according to charging documents.

Mr. Chauvin survived the attack.

In addition to the attempted murder charge, Mr. Turscak was charged with assault with intent to commit murder, assault with a dangerous weapon and assault resulting in a serious bodily injury, federal prosecutors said in a news release.

It was unclear on Friday if Mr. Turscak had a lawyer and what sentence he was serving in prison.

The charges related to attempted murder each carry maximum sentences of 20 years in prison, while the assault charges each have a maximum of 10 years, prosecutors said.

Mr. Chauvin, a former Minneapolis police officer who is white, murdered Mr. Floyd, who is Black, during an arrest on a South Minneapolis street corner in May 2020.

Mr. Chauvin knelt on Mr. Floyd for nine and a half minutes as Mr. Floyd was handcuffed, face down on the street.

The killing of Mr. Floyd was captured on video and set off the largest protests in a generation against police violence and racism.

Mr. Chauvin is serving a sentence of 22 and a half years on the state murder charges, and a concurrent sentence of just over 20 years for violating Mr. Floyd’s constitutional rights.

Glenn Thrush contributed reporting.