A witness in the shooting of an unarmed black teenager by a white police officer said Wednesday he saw the officer standing on the sidewalk, panicking, saying, "I don't know why I shot him. I don't know why I fired."

The trial of former East Pittsburgh Police Officer Michael Rosfeld ended for the day Wednesday in a Pittsburgh courtroom. It will reconvene Thursday morning.

John Leach, a neighbor who lives a few houses from the site of the June shooting, said he was on his front porch when Rosfeld fired three bullets into 17-year-old Antwon Rose II after pulling over an unlicensed taxicab suspected to have been used in a drive-by shooting minutes earlier. Rose was a front-seat passenger in the cab and was shot as he fled.

Rosfeld, 30, faces a charge of criminal homicide.

Leach, the second witness to testify Wednesday, said that after the shooting, he was watching Rosfeld on the sidewalk nearby saying repeatedly, "I don't know why I shot him. I don't know why I fired."

He said that later, he saw other officers consoling Rosfeld as he was crying, bent over and hyperventilating. Rosfeld, he said, looked as if he was about to pass out.

Defense attorney Patrick Thomassey had tried to discredit Leach's testimony, asking him if he was trying to "juice things up." Leach said, "I don't have any reason to."

Patrick Shattuck said Wednesday he was standing outside a senior center when Rosfeld pulled over the unlicensed cab in front of the building. Five to seven minutes after the shooting, Shattuck said Rosfeld, with swollen, red eyes, entered the building and said, "Why did he do that? Why did he do that? Why did he take that out of his pocket?"

East Pittsburgh Mayor Louis J. Payne, who was also there, said he, too, heard Rosfeld say, "Why did he do that?" but said he didn't hear the comment about the pocket.

Rosfeld was in the senior center only a few minutes when another officer came in and told him he couldn't be there. Rosfeld left, taking with him a rifle he had brought inside, Shattuck said.

Thomassey said Rosfeld did not intend to shoot anyone that day and did nothing wrong in his fatal encounter with Rose.

"You think Michael Rosfeld got up on the 19th of June and thought he was going to shoot someone? Of course not," he said.

Allegheny County Housing Authority officer Charles Rozzo, who responded to the shooting, testified that a distraught Rosfeld asked him how Rose was and if he "saw the gun." It's unclear what Rosfeld was referring to. Prosecutors said Rosfeld gave inconsistent statements about the shooting, including whether he thought Rose had a gun.

Authorities have said two guns were inside the vehicle and an empty magazine was in his pocket. One of the guns had Rose's DNA on it but does not appear to have been fired officials said.

The video of the shooting, recorded by neighbor Lashaun Livingston, was posted online, triggering protests in the Pittsburgh area last year, including a late-night march that shut down a major highway.

A jury of six men and six women, including three African-Americans, was selected across the state in Harrisburg last week and will be sequestered in a Pittsburgh hotel for the duration of the trial, expected to take a week or more.

Additional video was shown in court, taken by a University of Pittsburgh student who was in his car at a stop sign nearby. Peyton Deri said he couldn't really see whether there was anything in the hands of Rose or the vehicle's other occupant, Zaijuan Hester.

Rose's mother sent a letter to prosecutors Wednesday urging them to counter the defense's portrayal of her son as "just another thug." In the letter, she asks prosecutors to paint a picture of her son as he truly was.

"He was a rose that grew from concrete. Despite darkness all around him, he was kind, loving and funny," she wrote in the letter dated Tuesday.

She describes how he taught other children in the neighborhood how to Rollerblade and skateboard, and even gave away his skates to kids in need.

Rose had been riding in the front seat of the unlicensed taxi when Hester, in the backseat, rolled down a window and shot at two men on the street.

Hester, 18, of Swissvale, pleaded guilty Friday to aggravated assault and firearms violations for the shooting, which wounded a man in the abdomen. Hester told a judge that he, not Rose, did the shooting.