Just as his trial for attempted murder was about to begin, a 20-year-old West Philadelphia man pleaded guilty yesterday to shooting a rookie police officer in the face during a road stop eight months ago.

Officer Richard Decoatsworth, 22, who chased the gunman for three blocks before collapsing, kept his emotions in check in the courtroom as Antonio Coulter admitted shooting him on Sept. 24.

Coulter pleaded guilty to nine counts, including attempted murder and aggravated assault.

Common Pleas Court Judge Glenn Benson set sentencing for June 25. Coulter faces 40 years in prison on the attempted-murder charge.

Assistant District Attorney Mark Levenberg told the court that if the case had gone to trial, he would have called more than two dozen witnesses, including three teens who were in Coulter's car seconds before Coulter fired a sawed-off shotgun into Decoatsworth's face.

He also planned to introduce testimony that a month before the shooting, Coulter told a cousin he did not want to get "live-stopped anymore" by police and would shoot the next officer who tried.

In his statement to police, Coulter said he shot Decoatsworth because he thought the officer had seen the weapon and he "didn't want to get arrested."

Decoatsworth would have testified that he did not see or hear the shotgun blast, "but felt he had been hit in the face with a sledgehammer," the prosecutor said.

The officer was the first of six wounded by gunfire over two months last fall, including Officer Chuck Cassidy, who died.

Michael Graves, Coulter's attorney, said outside court that his client "decided he wanted to take responsibility for what happened."

Coulter had picked up three teen acquaintances who had had been locked out of school after arriving late and who were headed to his house to play video games when he caught the attention of Decoatsworth.

Coulter pulled over at Farson Street near Arch Street and told the teens to get out of his car. Decoatsworth left his cruiser and told the youths to come back.

They were returning when Coulter stood up at the driver's door of his car and fired at the officer. In his statement, Coulter said he was aiming for Decoatsworth's head.

Although wounded, the officer gave chase, firing at least seven shots but not hitting Coulter.

Police found Coulter hiding in a yard near where Decoatsworth had collapsed. The 12-gauge shotgun was found hidden under debris.

"It was tough being in there," Decoatsworth, who has undergone four operations on his face, with more to come, said after the hearing yesterday.

"I'm a human being. You get upset, you get emotional, you get angry, but . . . you've got to tuck those things away. That's one of the hardest things to do on this job, keep your emotions aside from your work, and that's what I did."

Decoatsworth plans to return to the force on limited duty soon but has not decided what he will do after that except to resume his career in the department.

Contact staff writer Joseph Gambardello at 215-854-2153 or jgambardello@phillynews.com.