The convenience store cashier who sold cigarettes to George Floyd and was handed a counterfeit $20 bill said he felt "disbelief - and guilt" as he watched the arrest unfold.
Christopher Martin, 19, was captured on CCTV standing on the curb looking on at the scene with his hands on his head alongside a small crowd of onlookers during the incident on May 25 last year.
Asked by Assistant Attorney General Matthew Frank why he felt guilt, Mr Martin said: "If I would’ve just not [taken] the bill, this could’ve been avoided."
Surveillance inside the Cup Foods store in Minneapolis was played to jurors at the Hennepin County Government Center where former Police Officer Derek Chauvin is on trial for murder.
It showed Mr Floyd interacting with staff and other customers for approximately 10 minutes before he was served at the tobacco counter by Mr Martin.
Mr Martin, who lived in an apartment above the store at the time with his mother, said he had been working at the Cup Foods for several months before the incident.
But he said he stopped working at the store shortly after the incident as he "feared for his safety" and felt "too guilty".
Asked about his interaction with Mr Floyd, he said he said he "appeared to be high" but was "friendly" and "approachable".
"I asked him if he played baseball and he played football," he said.
"When I asked him if he played baseball, he went on to respond to that but it kind of took him a little long to get to what he was trying to say so it would appear that he was high."
Martin said he immediately believed the $20 that Floyd gave him was fake due to it having a "blue pigment", but accepted it "to do him a favour" even though store policy was that the amount would be taken out of his paycheck.
"When I saw the bill I saw it had a blue pigment to it, kind of like a $100 has so I thought that was odd," he said.
"I took it anyways and I was planning to just put it on my tab until I second guessed myself and as you can see from the video I kept examining it and then I told my manager."
He told the court that he had refused a counterfeit bill earlier that day when serving Mr Floyd's male friend.
He said his manager sent him outside to Mr Floyd's car to ask him to return to the store.
Mr Martin said he tried twice to get Mr Floyd and his friends to come back into the store to speak with a manager about the bill, but they refused.
A manager then directed another employee to call the police.
Once the police arrived, the cashier watched as the encounter escalated and a crowd of people formed shouting at officers to let Mr Floyd up and check his vital signs.
“I saw people yelling and screaming,” he said. “I saw Derek [Chauvin] with his knee on George [Floyd]’s neck on the ground.”
The court has heard that Chauvin pinned his knee on his neck for what prosecutors said was nine minutes, 29 seconds, as a handcuffed Floyd lay face-down on the pavement.
Mr Martin said he took out his phone and began recording, but later deleted it, explaining that the ambulance didn’t take the fastest route to the hospital so he presumed Floyd had died.
“I just didn’t want to have to show it (the video) to anyone,” he said.
Mr Floyd, 46, was pronounced dead at a hospital. The defence has argued that the now-fired officer did what his training told him to do and that Floyd’s death was not caused by Chauvin's knee on his neck, as prosecutors contend, but by a combination of illegal drug use, heart disease, high blood pressure and the adrenaline flowing through his body.