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The former Minneapolis Police officer who pressed his knee into George Floyd’s neck was charged on Wednesday with a new, more serious count of second-degree murder, and the three other officers on scene during his killing were charged with aiding and abetting second-degree murder.

“I strongly believe that these developments are in the interest of justice for Mr. Floyd, his family, our community and our state,” Minnesota Attorney General Keith Ellison said in announcing the charges.

The announcement came more than a week after Floyd was killed while in police custody in Minneapolis, sparking nationwide protests that call for the end to police violence against black citizens.

Derek Chauvin, who pressed his knee into Floyd’s neck for nearly nine minutes, was previously charged with third-degree murder and second-degree manslaughter. The new second-degree murder charge says he killed Floyd “without intent” in the course of committing assault in the third degree, according to an amended complaint.

Derek Chauvin, J. Alexander Kueng, Thomas Lane and Tou Thao face charges in the death of George Floyd.

Thomas Lane and J. Alexander Kueng, who helped restrain Floyd, and Tou Thao, who stood near the others, were not initially charged. Lane, 37, Kueng, 26, and Thao, 34, are now charged with aiding and abetting second-degree murder and aiding and abetting second-degree manslaughter.

Chauvin, 44, was arrested last week and is being held at the Minnesota Department of Corrections facility in Oak Park. His bail was increased to $1 million Wednesday, court documents show.

Lane, Kueng and Thao were taken into custody Wednesday and are being held on $1 million bail, county jail records show.

Kueng’s attorney, Tom Plunkett, said in a statement that his client “was asked to turn himself in to face charges” Wednesday afternoon and was in custody 15 minutes later.

Second-degree murder and aiding and abetting second-degree murder are punishable by up to 40 years in prison. Manslaughter and aiding and abetting manslaughter are punishable by up to 10 years in prison.

George Floyd died while in police custody May 25 in Minneapolis.

Two autopsies on Floyd determined that he died by homicide. Minneapolis Police Chief Medaria Arradondo fired the four officers and said they were “complicit” in Floyd’s death, and Floyd’s family and protesters nationwide have called for them to be arrested and convicted for the killing.

According to the video and the criminal complaint, Chauvin kept his knee on Floyd’s neck as Floyd pleaded that he could not breathe, as witnesses protested that he was dying, and even as Lane twice asked to turn him onto his side. Still, Chauvin kept his knee in position for almost three minutes after Floyd became unresponsive, the complaint states.

Family says charges are bittersweet

Benjamin Crump, an attorney for the Floyd family, said on Twitter that the family was gratified with the new charges.

“FAMILY REACTION: This is a bittersweet moment. We are deeply gratified that (Ellison) took decisive action, arresting & charging ALL the officers involved in #GeorgeFloyd’s death & upgrading the charge against Derek Chauvin to felony second-degree murder,” he said.

Still, he said that he believes Chauvin should be charged with first-degree murder, which requires intent, and the charges only represent the first steps toward justice.

“We cannot celebrate because an arrest is not a conviction and we want justice,” Crump told reporters on Wednesday. “We want whole justice.”

Crump noted neither he or the family have reviewed the footage from the officers body cameras.

At the news conference, Ellison insisted that the protests did not influence the charges.

“I did not allow public pressure to impact our decision-making process,” he said. “We made these decisions based on the facts that we gathered since this matter occurred and made these charges based on the law that we think applies.”

Ellison was appointed by Gov. Tim Walz to take over the case from Hennepin County Attorney Mike Freeman on Sunday.

A former Democratic congressman, Ellison had cautioned against a rush to judgment, citing the difficulty of prosecuting police officers.

Officers are rarely charged with crimes for violence against black men, and even in those rare cases, juries have repeatedly shown an unwillingness to convict. The list of such failed cases is long.

In 2017, for example, the Minnesota police officer who fatally shot Philando Castile was found not guilty of second-degree manslaughter and intentional discharge of firearm that endangers safety.

“We’re confident in what we’re doing, but history does show that there are clear challenges here,” Ellison said.

Walz said in a statement that the new charges are a meaningful step.

“The charges announced by Attorney General Keith Ellison today are a meaningful step toward justice for George Floyd. But we must also recognize that the anguish driving protests around the world is about more than one tragic incident,” he said.

“George Floyd’s death is the symptom of a disease. We will not wake up one day and have the disease of systemic racism cured for us. This is on each of us to solve together, and we have hard work ahead. We owe that much to George Floyd, and we owe that much to each other.”

CNN’s Konstantin Toropin, Andy Rose, Nicole Chavez, Kara Devlin and Gregory Lemos contributed to this report.