Originally Published: 15 AUG 22 13:03 ET

By Claire Colbert, Bill Kirkos and Brad Parks, CNN

(CNN) -- Ex-Minneapolis police officers J. Alexander Kueng and Tou Thao told a judge Monday they have rejected a plea deal offered by state prosecutors for their role in George Floyd's killing, Minnesota Attorney General Keith Ellison's deputy chief of staff said.

Their trial, set to begin October 24, marks the latest chapter in a case that in May 2020 catalyzed a nation's anger over how some in law enforcement treat people of color.

Kueng and Thao -- already awaiting sentencing on federal convictions -- are charged with aiding and abetting second-degree unintentional murder and aiding and abetting second-degree manslaughter for their role in the fatal restraint of Floyd on a Minneapolis street. They have pleaded not guilty.

Kueng and Thao both were offered the same plea deal former officer Thomas Lane accepted earlier this year, said Ellison's deputy, John Stiles. Lane pleaded guilty in June to aiding and abetting second-degree manslaughter and is set to be sentenced on September 21, with the parties jointly recommending "a sentence of 36 months, which in Minnesota ... typically means 24 months-time actually served," Stiles said.

CNN has reached out to attorneys representing Kueng and Thao for further comment.

The charges stem from the former officers' actions -- or lack thereof -- as their colleague Derek Chauvin pressed his knee into the neck and back of Floyd, a 46-year-old Black man who was handcuffed and lying on his stomach, for over nine minutes on May 25, 2020.

During the arrest, Lane held down Floyd's legs, Kueng held down Floyd's torso, and Thao stood nearby and kept back a crowd of upset bystanders. Harrowing video taken by a bystander showed Floyd desperately pleading for them to let him breathe and calling for his mother before he lost consciousness and died.

Chauvin was convicted last spring of Floyd's murder in a state trial and was sentenced to more than 22 years in prison. He also pleaded guilty in federal court in December to violating Floyd's civil rights and has been sentenced to 21 years in prison.

Kueng, Lane and Thao were convicted in federal court in February of violating Floyd's civil rights. Kueng was sentenced to three years in prison; Thao was sentenced to 3-1/2 years in prison; and Lane was sentenced to 2-1/2 years in prison.