Three more former Minneapolis police officers were charged Wednesday in the death of George Floyd, five days after charges were brought against a fourth officer who was seen in a video kneeling on Floyd’s neck.

The three former officers, Tou Thao, Thomas Lane and J. Alexander Kueng, were charged with aiding and abetting murder, according to criminal complaints filed by the state of Minnesota. The murder charge against the fourth, Derek Chauvin, was also elevated to second-degree, from third-degree.

Chauvin, who held his knee on Floyd’s neck for more than eight minutes while detaining him on May 25, was also initially charged Friday with manslaughter by the Hennepin County prosecutor. He still faces both the third-degree and manslaughter charges as well, according to an amended complaint.

All four officers were fired on May 26, after a video showing Floyd's arrest went viral.

An attorney for Kueng said in a statement that the former officer turned himself in at about 1:35 p.m. local time. The two other officers were in the process of being placed in custody, officials said Wednesday.

All four of the men face a maximum sentence of 40 years in prison, according to the criminal complaints.

The Minnesota Fraternal Order of Police did not immediately respond to a request for comment on the elevated murder charge against Chauvin or the charges filed against the other three officers Wednesday. It was not immediately clear if Lane and Thao had retained lawyers.

Minnesota Attorney General Keith Ellison asked the community for continued patience on Wednesday as his team of prosecutors investigate the case, noting that prosecution of police officers for such a charge is a difficult task.

"I feel a tremendous sense of weight, I feel that this is a very serious moment," Ellison said. "I can tell you I feel no joy in this, but I do feel a tremendous sense of duty and responsibility."