Minnesota Attorney General Keith Ellison said Wednesday at a news conference that all four Minneapolis police officers involved in the killing of 46-year-old African-American George Floyd will face criminal charges. Floyd was killed on May 25, after officer Derek Chauvin pressed his knee on Floyd’s neck for nearly nine minutes during an arrest. 

Chavin had been charged with third-degree murder and second-degree manslaughter. Ellison said Chauvin’s murder charge was upgraded to second-degree murder. The three other officers on the scene— Tou Thao, J. Alexander Kueng and Thomas Lane — are also charged with aiding and abetting murder.

Video showed Lane and Kueng had helped restrain Floyd, while Thao stood near the others. Floyd was arrested for reportedly using a counterfeit $20 bill at a nearby deli.

“In order to be thorough, this is going to take months,” Ellison said about the investigation into the killing. “I don’t know how many, but it is better to make sure that we have a solid case -- fully investigated, researched -- before we got to trial than to rush it.”

Ellison has asked for the bail for all four officers to be set at $1 million. Floyd’s family has called the charges “bittersweet” and requested first-degree murder charges for Chauvin. 

“This is another important step for justice,” Sen. Amy Klobuchar, D-Minn., said of the charges.

A Minneapolis group, Communities United Against Police Brutality, had reported that Klobuchard failed to bring charges against Chauvin while serving as a prosecutor in 2006. 

Protests across the U.S. have erupted since Floyd’s killing, with multiple cities imposing curfews. Looting and violence have erupted in some cities, while President Trump has threatened to deploy the military if states fail to quell the violence.