An Uber driver testified yesterday about the snowy morning in South Boston when an allegedly intoxicated off-duty cop attacked him from the back seat, clawing at his face, pummeling him in the ribs — even threatening to kill him, Luis Blanco claimed.

“He said, ‘You think I’m an idiot? I’m going to kill you, you (expletive) (racial slur)!’ He was punching me, he grabbed my ear. He was trying to grab my face from behind me,” Blanco said of Michael C. Doherty, 43, who the Boston Police Department suspended without pay following his arrest on assault, civil rights and motor vehicle charges for the 2015 confrontation.

The confidence Blanco exhibited on the witness stand in Suffolk Superior Judge Linda E. Giles’ courtroom was in sharp contrast to the panicked 911 call he made while trying to escape Doherty, and which assistant Suffolk District Attorney Andrew Doherty played yesterday for jurors.

Blanco, 31, who helps run his family’s South End convenience store, testified that at one point Doherty was chasing him around his Toyota Prius. He just didn’t know why.

Blanco said he typically drives for Uber and Lyft between noon and 3 a.m. He picked up a short, stocky man named “Michael” and a male buddy outside Bricco restaurant in the North End in the early morning hours of Jan. 4, 2015.

“They were under the influence, jovial, just a good time, or whatever,” Blanco said.

After dropping the buddy off in Charlestown, Blanco said Doherty asked to go to East Second Street in South Boston, but when they arrived, he began throwing a fit.

“He began to say, ‘Take me someplace else.’ He said, ‘Go, go, go!’ He started shouting. He was becoming very angry,” Blanco recalled.

When Blanco wriggled out of both his seat belt and his jacket at an intersection, he frantically flagged down the first car he saw. But as the driver — who turned out to be a fellow Uber operator named Guilliano Verna, 32 — stopped to help, Blanco said Doherty took off with his Prius.

“I said, ‘Help me, help me, he just stole my car!’ I didn’t wait for him to answer, I just jumped in the back seat of his car,” Blanco said of Verna, whom he had never met.

Verna also testified yesterday, telling jurors how he and Blanco caught up to Doherty when he pulled over a few blocks away.

Before they got into a scuffle, Verna said Doherty told him, “Get the (expletive) out of here, (racial slur). Do you know where you’re at? This is South Boston.”