Federal prosecutors have been mounting a case against former Minneapolis police officer Derek Chauvin and the three other ex-cops involved in the call that led to the death of George Floyd, with the intention of indicting the quartet on civil rights charges, according to a report.

The Star Tribune cited a source in reporting that prosecutors with the U.S. Attorney’s Office intend to indict Chauvin, who was convicted of murder earlier this month, and former Minneapolis police officers Thomas Lane, Tou Thao and J. Alexander Kueng for violating Floyd’s civil rights.

The charges, if a grand jury chooses to indict, would be in addition to the state charges of aiding and abetting both second-degree murder and second-degree manslaughter, for which the trio is expected to stand trial in August, according to the report.

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The Tribune also described how U.S. Department of Justice officials planned to arrest Chauvin at Hennepin County Courthouse earlier this month if the judge declared a mistrial, or if the jury announced a verdict had found the 45-year-old former officer not guilty.

Floyd, a 46-year-old Black man, died after Chauvin, who is White, held his knee against Floyd’s neck for more than nine minutes — as Floyd was handcuffed and face-down on the pavement and despite his repeated shouts that he could not breathe.

Chauvin stood trial for weeks, starting earlier this month, in connection with Floyd’s death.

On April 20, a jury found Chauvin guilty of second-degree unintentional murder, third-degree murder and second-degree manslaughter. He faces decades behind bars at his sentencing, which is scheduled for June 25.

Charges for the federal case would only be brought against Chauvin and would also involve a 2017 incident in which he allegedly violently handled a 14-year-old boy and used his knee to hold the teenager down for almost 17 minutes, according to the Tribune and a previous ABC News report.

Video of the arrest allegedly shows Chauvin aggressively handling the teenager while the now-ex-cop was responding to a domestic violence call with another cop in September 2017, according to the report. The teenager was reportedly one of two people accused of assaulting his mother.

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ABC News reported that the footage allegedly depicted Chauvin striking the 14-year-old’s head after he wouldn’t comply with officers. Chauvin allegedly struck the teen with a flashlight twice and held the boy’s throat, according to the report. He then "applied a neck restraint, causing the child to lose consciousness and go to the ground," state prosecutor Matthew Frank wrote in court papers, according to ABC.

Former Minneapolis police officers Derek Chauvin, J. Alexander Kueng, Thomas Lane and Tou Thao. 

Former Minneapolis police officers Derek Chauvin, J. Alexander Kueng, Thomas Lane and Tou Thao.  (Hennepin County Sheriff's Office via AP)

"Chauvin and [the other officer] placed [the teenager] in the prone position and handcuffed him behind his back while the teenager's mother pleaded with them not to kill her son and told her son to stop resisting," Frank wrote, according to the report. "About a minute after going to the ground, the child began repeatedly telling the officers that he could not breathe, and his mother told Chauvin to take his knee off her son."

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He allegedly adjusted his knee after eight minutes, and placed it on the boy’s upper back for another nine minutes, Frank wrote.

The teen was arrested for obstruction with force and domestic assault, ABC News reported. He began bleeding from his ears during the allegedly violent arrest and ultimately needed stitches, Frank wrote.

"Just like with Floyd, Chauvin used an unreasonable amount of force without regard for the need for that level of force or the victim's well-being," Frank reportedly wrote. "Just like with Floyd, when the child was slow to comply with Chauvin and [the other officer's] instructions, Chauvin grabbed the child by the throat, forced him to the ground in the prone position, and placed his knee on the child's neck with so much force that the child began to cry out in pain and tell Chauvin he could not breathe."

The Associated Press contributed to this report.