As his brother’s killer was sentenced to life in prison today, a 12-year-old boy threw down a gauntlet and urged adults to “step up and help the younger generation so they don’t follow the wrong path to the streets.”

The boy’s heartfelt plea came in a victim-witness impact statement he delivered following the second-degree murder conviction of JAMES “GUNNA” WALKER (D.O.B. 9/9/86) for shooting 20-year-old Antoine Perkins to death four years ago. Walker was convicted Wednesday.

“As brave as he was, it’s terribly sad to see such maturity forced upon a child so young,” said Suffolk County District Attorney Daniel F. Conley, whose office prosecuted Walker. “We have to take his words to heart, nurture our children, and prove that there are goals and accomplishments far greater than any they’ll find in a gang.”

Assistant District Attorney Edward Krippendorf of Conley’s Homicide Unit proved during the week-long trial that Walker, a notorious member of the Lucerne Street Doggz street gang, stole two pounds of marijuana from a drug dealer in a June 2006 transaction Perkins had facilitated. Krippendorf also proved that Perkins later led the dealer’s associates to Walker’s home, and that those associates fired shots at the residence.

No one was injured, the evidence showed, but Walker considered Perkins to be “a snitch” for his actions. On June 23, the evidence established, Walker approached Perkins as he sat on the steps of his Morton Street home. Walker shot Perkins in the head, inflicting an injury that would claim Perkins’ life at Boston Medical Center.

In his impact statement, Perkins’ younger brother also said he had a duty to raise and protect his younger family members.

“Now that Antoine is gone and my nephew does not have a father, it is my job and his godfather’s job to help him not follow that path of the person that took him away,” he said to a packed courtroom.

Katherine Moran was the DA’s assigned victim-witness advocate. Walker was represented by attorney James Budreau.