"This is what I saw," Williams said, after Minnesota Assistant Attorney General Matthew Frank displayed a now-famous photo of Chauvin holding his knee on Floyd's neck. In the photo, Chauvin is looking up at the camera.
"The only reason why he's looking at me right now is because I told him it was a 'blood choke,'" Williams told Frank, who is leading the prosecution.
When asked what he heard from Floyd, Williams said the man was in distress, repeatedly saying that he couldn't breathe and that he was in pain. Floyd also said he was sorry, Williams recalled. He later said that at the time, he didn't know Floyd's name.
With Frank asking questions, he discussed his experience with choke holds and the practice of "tapping out" when a fighter submits.
He also said he saw Chauvin use a "shimmy" hold on Floyd, to restrict his motions.
Williams had gone fishing with his son earlier on May 25, and he said that after struggling to remember how to cut their catch up, he decided to get some air and pick up something to drink from Cup Foods. But as he walked toward the door, he saw two police vehicles outside. He started to wonder if perhaps he should just leave. He never made it inside.
"My energy stopped me, the surroundings stopped me," Williams said. "The energy of the air ... the energy was off. I couldn't like, get in the door for some reason."
As he watched the police actions taking place outside Cup Foods, Williams said he wondered, "Should I involve myself?"
He started hearing people talking and yelling, as officers struggled with George Floyd. Someone was saying to calm down. Another person called for their mother, he said. And one voice was saying, "Let him up."
The court saw a still photo from a surveillance video, showing Williams walking toward the door of the store, with the police in the street and several bystanders standing along the edge of the sidewalk.
"I observed the scene first before I spoke," Williams said.
An older man was calling out to Floyd, telling him that it would be OK and not to resist arrest, Williams said. Bystanders also told police they were concerned.
He says he also heard "George, on the ground, pretty much pleading for his life."
Williams walked closer to the commotion, moving to the edge of the street. As he recalls, he was "battling with myself to stay on the curb" as he watched what transpired.
Williams said he called former officer Tou Thou by his last name because he was close enough to read it on the officer's badge. As for what Thou's role was, he said, "He was the dictator," controlling what happened along the curb.
"He was the guy that let it go on," Williams said. Tou and two other officers will be tried separately on charges of aiding and abetting.
"I was totally scared for my safety and those around me," Williams said as he continued his testimony Tuesday.
He said he grew emotional because of the situation – and also because of how police were behaving. They were "nonresponsive" to his and other onlookers' concerns, he said.
He added that after the ambulance arrived, Chauvin did not take his knee off of Floyd's neck. After Floyd was loaded onto a gurney and taken away in an ambulance, Williams lingered.
He was nervous, he said, and didn't know what to do. He saw the officers move across the front of the store, away from the scene. Williams then pulled up his cellphone, called 911 – and reported to the dispatcher that he had just seen a murder. He said he felt the need "to call the police on the police."
The prosecution then played the recording of Williams' 911 call in court. "That was bogus, what they just did," Williams told the dispatcher.
In the emergency call, Williams singled out one officer by his badge number – he was referring to Chauvin, he acknowledged as he pointed to the former officer in court.
Jury In Chauvin Trial Hears More From Witness About 'Blood Choke'
