As the second day of Derek Chauvin’s murder trial began on Tuesday morning (March 30), witness Donald Williams took the stand. Williams is the third witness in the trial and began his testimony on Monday (March 29), but was cut off abruptly due to technical issues.

As reported by REVOLT, Williams is a professional mixed martial arts fighter who was at the scene of George Floyd’s fatal interactions with Minneapolis police officers on May 25. While being questioned by the prosecution, Williams was asked to recount the events he witnessed that day.

“You could see that he was going through tremendous pain,” Williams said of Floyd. “You could see it in his face from the grunting; you could see his eyes slowly rolling back in his head…”

“You could see that he was trying to gasp for air,” he added.

Williams said that Chauvin’s and the other officers’ interactions with Floyd made him fear for his own safety.

“I felt like he was in very much danger,” he said. “Seeing another man like me being controlled… I was totally scared for my safety and the people around me.”

Williams called 911 after Floyd was taken away in an ambulance.

“I did call the police on the police,” he said in court. “Because I believe I witnessed a murder.”

Williams’ 911 call was played for the jury during the trial. On the stand, Williams began to tear up while reliving the traumatic incident.

During the call, Williams identified Chauvin by his badge number and said he was reporting the cop “for killing a citizen.”

“He just pretty much just killed this guy that wasn’t resisting arrest,” Williams told the 911 dispatcher. “He had his knee on the dude’s neck the whole time… The man stopped breathing. He wasn’t resisting arrest or nothing… They pretty much just killed the dude.”

At one point in the call, Williams says, “Y’all murderers, bro.”

The 911 dispatcher transferred Williams’ call so he could speak to a Sargeant. The call abruptly ends, though, as Williams said he felt intimidated by officer Tou Thao, who he says approached him with his body camera while he was on the phone.

Williams added that it was the officers’ lack of remorse that upset him the most.

“I felt the need to call the police on the police,” he said.

Chauvin is charged with second- and third-degree murder as well as second-degree manslaughter. Watch the second day of his trial live below.