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Grieving relatives said they can't understand why he was killed.
"He's so young, why would somebody want to do that? That's not right. People just pull out guns for no reason," said the victim's sister Treasure Porter.
"Now I only have one brother because somebody wants to be dumb," she said.
Police said Allen was standing outside in the 8800 block of South Broadway when somebody approached him just after 12:15 p.m. Sunday. They exchanged a few words before the suspect pulled out a gun and shot the teen twice in the chest.
The teen was taken to the hospital where he died from his injuries.
"We can't get him back, and whoever that is that did that, I just want to let you know, God don't like ugly. This was really senseless," said a family friend identified only as Sadella.
People who knew him said he was a good kid who got involved with the wrong crowd.
No one has been arrested. Police believe the gunman was a gang member.
"The circumstances that led up to it, it just fits for a gang walk-up," said LAPD Lt. Glenn Krejci.
The fatal shooting was just a couple of blocks from Victory Outreach Church, where former gang members have found support to change their lives.
"All it did for me was leave me in and out of juvenile hall, and it's brought a lot of pain and sorrow to my family," said former gang member Robert Ramirez.
Others in the community said there's a need for programs that keep kids out of gangs.
"We're not supposed to be burying our children. Our children (are) supposed to be burying us," said Dewon Young from Victory Outreach Church.
LAPD statistics show that in the last seven years gang-related homicides in the city have been on a steady decline. So far this year there have been 99 gang-related deaths. In the same time period in 2002, there were 240 deaths.
"The only way to stop this from happening is for the community to come together and not stand for this any longer," said Krejci. "They need to tell us what happened and help us catch the people that did it so they're the ones that are afraid, not the community that is victimized by these gang members."
Police say they know there are witnesses out there that can help them identify the shooter. Anyone with information is urged to call LAPD at (877) LAPD-24-7.