Updated

A man's own surveillance camera video shows him gunning down a 13-year-old neighbor in Milwaukee.

Seventy-six-year-old John Henry Spooner is on trial in the May 2012 death of Darius Simmons, whom Spooner had accused of breaking into his house and stealing his guns.

Spooner's attorney says he client has a mental illness.

Surveillance video taken from Spooner's own home shows him confronting Simmons, pointing a gun at him and shooting him in the chest. The boy stumbles and runs away, and Spooner fires a second shot that misses him.

Simmons' mother testified that Spooner warned her to call 911 and accused her son of burglarizing his home. She said Spooner told her son he'd teach him not to steal, and then fired the shot the struck the boy in his chest.

Patricia Larry testified tearfully that as she held her son, "He took one more breath and that's it."

Spooner is on trial for first-degree intentional homicide.