The cop is Texas had the authority to use lethal force but he chose not to. Officers in Texas are allowed to use deadly force if they reasonably believe deadly force is necessary to stop the loss of life. There's a pretty big difference between a cop kneeling on a handcuffed man for 15 minutes and a cop letting a heavily armed man waltz into a school.
The cop that killed George Floyd admitted that he ignored department policy. He admitted that he used unreasonable force. He admitted he continued to use force after Floyd was unconscious and not breathing.
"Chauvin admitted that on May 25, 2020, he willfully violated Mr. Floyd’s constitutional right to be free from an officer’s use of unreasonable force. Specifically, defendant Chauvin admitted that he held his left knee across Mr. Floyd’s neck, back and shoulder and his right knee on Mr. Floyd’s back and arm. The plea agreement states that Mr. Floyd remained restrained, prone and handcuffed on the ground for approximately 10 minutes. Defendant Chauvin further admitted that he continued to use force even though he was aware that Mr. Floyd had stopped resisting, talking and moving, and even though he was aware that Mr. Floyd had lost consciousness and a pulse. Defendant Chauvin admitted that Minneapolis Police Department (MPD) policy and training requires officers to stop using force when a subject is not resisting and to move an arrestee from the prone position into a side recovery or seated position because the prone position may make it more difficult to breathe. Defendant Chauvin admitted that his willful use of unreasonable force resulted in Mr. Floyd’s bodily injury and death because his actions impaired Mr. Floyd’s ability to obtain and maintain sufficient oxygen to sustain Mr. Floyd’s life. "
And it's not the first time he's done this.
"Chauvin admitted that he held the juvenile by the throat and struck the juvenile multiple times in the head with a flashlight, resulting in the juvenile’s bodily injury. In the plea agreement, defendant Chauvin also admitted that he held his knee on the juvenile’s neck, shoulders and upper back for between 15 and 16 minutes, even though the juvenile was face-down on the floor, handcuffed and not resisting"
Derek Chauvin committed an adult crime. So he's doing adult time.