An NYPD cop stoically recounted on the stand Wednesday the tragic moment that his partner, Randolph Holder, was gunned down during a foot chase in East Harlem.

“We started to walk toward him, and he decided to pull a gun outside his sweater,” Police Officer Omar Wallace told jurors of the deadly encounter with defendant Tyrone Howard on the 120th Street footbridge Oct. 20, 2015.

“He fired a shot, and that first shot hit Officer Holder in the right side of the head, and he fell immediately,” the cop recalled at Howard’s murder trial in Manhattan Supreme Court.

Wallace radioed for help as he returned fire, hitting Howard in the buttocks and leg as he fled north on the East River Promenade. Wallace turned back to tend to his partner, who lay dying in a pool of blood. Howard, 33, was later captured near 124th Street.

At one point, prosecutors asked Wallace to identify Howard in the courtroom.

“Right over there,” he said as Howard, his eyes glued to the defense table, vigorously scribbled notes. “He isn’t looking at me,” he added.

Wallace’s calm, emotionless demeanor on the stand contrasted with his frenzied radio call for help that was played in court.