MILWAUKEE — A Milwaukee man who killed his 13-year-old neighbor last year testified Thursday the shooting was "justice" because he thought the teen had broken into his home and stolen weapons.

John Henry Spooner, 76, said the suspicion that Darius Simmons stole expensive shotguns of deep sentimental value left him "very, very angry." Police searched Darius' home after the shooting and didn't find the weapons.

A prosecutor alleged that Spooner traded the boy's life for guns in a desire for revenge.

"I wouldn't call it revenge. I would call it justice," Spooner said defiantly, drawing audible gasps from the courtroom. Darius' mother, Patricia Larry, threw up her hands and muttered, "Oh my god."

Spooner was testifying against the advice of his lawyer. Defense attorney Franklyn Gimbel told the judge during morning proceedings that his client had suddenly lost the mental competence to continue with the trial. The judge halted proceedings for a few hours until a court-appointed psychiatrist performed a brief examination and pronounced Spooner competent to continue.

Spooner was convicted Wednesday of first-degree intentional homicide. That verdict advanced the trial to a second phase to determine whether Spooner was sane at the time of the May 2012 shooting. The second phase was expected to wrap up Friday with testimony from a doctor hired by the prosecution. A doctor retained by the defense testified Wednesday that Spooner had anger issues that caused him to periodically detach from reality.

If the same jurors who convicted Spooner decide he was competent, he'll face life in prison. If they conclude he was mentally ill, he could be committed.

Spooner didn't testify in the first phase. The judge asked him Thursday if he wanted to testify in the second phase, and Spooner said he'd prefer to give a 15-minute statement. When told he could only address the jury in the form of sworn testimony and cross-examination, he agreed to take the stand.

Spooner mostly spoke in a calm voice but sounded anguished as he recounted how he confronted Darius and shot him in the chest. He recalled that someone had stolen four shotguns from his home two days earlier, and he was frustrated by a limited police response.

Gimbel asked him what caused him to shoot the boy.

"I wanted my guns back," Spooner replied, squeezing his eyes shut and resting his head against his fingertips. "I just wanted them back so bad."

Spooner never denied shooting Darius, and acknowledged wanting to kill the teen's older brother as well. Theodore Larry, 18, had rushed into the street to help his wounded brother.

"If there weren't other people behind him you would have shot him," prosecutor Mark Williams offered.

"I would have shot him," Spooner replied.

The strongest piece of evidence against Spooner was footage from his own surveillance cameras, which showed him confronting Darius on the sidewalk and pointing a handgun at him. The boy backpedaled a few steps with his hands up. Spooner then exchanged words with Darius' mother on her porch off screen, and then turned and fired one shot at Darius' chest.

The teen fled, and Spooner fired a second shot that missed. He tried to shoot a third time but the gun jammed.

Darius died a few moments later across the street, in his mother's arms.

Gimbel conceded from the outset that Spooner killed the boy, but argued during the first phase that the homicide may have been reckless but not intentional, because Spooner didn't mean for the shot to be fatal. The jury deliberated for about an hour Wednesday before rejecting that argument.

Spooner had entered two pleas to the homicide charge: not guilty and not guilty by reason of mental disease or defect. That set up the trial to be conducted in two phases: the first to determine whether he was guilty of the homicide, and if so, a second to determine whether he was mentally competent at the time.

While Spooner didn't deny what he did, he had a hard time explaining to the prosecutor why he did it.

When Williams asked if he took the safety off the gun because he wanted to kill the boy, Spooner said he didn't know. Williams asked why Spooner fired a second time and Spooner again said he didn't know.

Finally, Williams asked whether Spooner felt bad about taking Darius' life.

"Not that bad," he replied softly.