PITTSBURGH (AP) — 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 continued into a second day Wednesday in a Pittsburgh courtroom where three witnesses were called during morning testimony.

John Leach, a neighbor who lives a few houses away from where the June shooting took place, said he was on the front porch when Rosfeld fired three bullets into 17-year-old Anton 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 after the shooting, he was standing by Rose's body, 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 later, he saw other officers consoling Rosfeld as he was crying, bent over, and hyperventilating. He said Rosfeld looked like he was about to pass out.

Leach said he saw Rosfeld pointing a gun at Rose while at least one of Rose's hands was in the air. Then, Rose turned and ran, he said.

Defense attorney Patrick 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.

Prosecutors said Rosfeld gave inconsistent statements about the shooting, including whether he thought Rose had a gun.

The video of the shooting, shot 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 about 600 feet (183 meters) away, the defense said. Peyton Deri said he couldn't really see if there was anything in the hands of Rose or the vehicle's other occupant, Zaijuan Hester.

The families of Rose and Rosfeld were in the courtroom Tuesday.

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 writes in the letter dated Tuesday. "The smile that emanates from photos of him truly reflects who he was."

She goes on to describe how he taught other children in the neighborhood how to roller blade and skateboard, and even gave away his skates to kids in need.

Rose had been riding in the front seat of the unlicensed taxicab 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.