MINNEAPOLIS — A former Minneapolis police officer pleaded guilty Monday to aiding and abetting second-degree manslaughter in the killing of George Floyd just as jury selection was about to begin, though another ex-officer was still headed to trial.

The plea deal for J. Alexander Kueng calls for 3 1/2 years in prison, with prosecutors agreeing to drop a count of aiding and abetting second-degree murder. Kueng is the second officer to plead guilty to the state charge, following Thomas Lane, who pleaded guilty earlier this year.

Their former colleague, Tou Thao, rejected a plea deal earlier this year, telling a judge it “would be lying” to accept any such deal. Jury selection for Thao was expected to begin later Monday.

All three were convicted in February on federal counts of willfully violating the civil rights of Floyd, who was Black. Lane was sentenced to 2 1/2 years in the federal case. Kueng was sentenced to three years and Thao was sentenced to 3 1/2, but for some Floyd family members and activists, the penalties were too small.

Floyd, 46, died May 25, 2020, after Officer Derek Chauvin, who is white, pinned him to the ground with a knee on Floyd’s neck as he repeatedly said he couldn’t breathe. The killing, captured on widely viewed bystander video, sparked protests in Minneapolis and around the globe as part of a reckoning over racial injustice.

Kueng and Lane helped to restrain Floyd, who was handcuffed. Kueng knelt on Floyd’s back and Lane held down Floyd’s legs. Thao kept bystanders from intervening during the 9 1/2-minute restraint.

As part of his plea agreement, Kueng admitted that he held Floyd’s torso, that he knew from his experience and training that restraining a handcuffed person in a prone position created a substantial risk, and that the restraint of Floyd was unreasonable under the circumstances.

Kueng’s plea called for him to serve his state and federal terms concurrently, just as Lane is doing.

Chauvin was convicted of state murder and manslaughter charges last year and is currently serving 22 1/2 years in the state case. He also pleaded guilty to a federal charge of violating Floyd’s civil rights and was sentenced to 21 years for that and for an unrelated case involving a 14-year-old boy. He is serving the sentences at the same time at the Federal Correctional Institution in Tucson, Arizona.

Kueng is Black, Lane is white and Thao is Hmong American. They were convicted of federal charges in February after a monthlong trial that focused on the officers’ training and the culture of the police department. All three were convicted of depriving Floyd of his right to medical care and Thao and Kueng were also convicted of failing to intervene to stop Chauvin during the killing.

After their federal sentences, there was a question as to whether Kueng and Thao would proceed to trial, with legal experts saying it was likely they’d seek a plea deal with the state that would not exceed the federal sentence and allow them serve both sentences at the same time.

State sentencing guidelines for a person with no criminal record, like Kueng, call for a range from about 3 1/2 years to four years and nine months in prison for second-degree unintentional manslaughter. The presumptive sentence is four years.

If Kueng had been convicted of aiding and abetting second-degree murder, he would have faced a presumptive 12 1/2 years in prison.