Transcript for Manhunt Underway for Little Rock Road Rage Shooter
Back here at home now, and to growing outrage and a growing reward at this hour, in that road rage manhunt in Arkansas. The FBI now joining the search for the gunman who killed a 3-year-old boy. Angry that the boy's grandmother was driving too slow. That grandmother not realizing her own grandson had even been shot until she pulled over at the JCPenney store. ABC's Phillip Mena is in little Rock. Reporter: Tonight, the FBI and Little Rock police in an all-out manhunt. Searching for the suspect accused of opening fire, killing this 3-year-old boy, acen king, in an apparent case of road rage. Bystanders calling 911. You can hear acen's grandmother, Kim king-may kcon, trying to describe the horror. Acen has been shot! Oh, my god! Reporter: It wasn't until she pulled into this JCPenney marking lot that she realized her grandson in the backseat was hit. I was at the stop sign and the guy blew the horn at me, and I blew it back and he shot, but I thought that he shot in the air. He shot at the car. Reporter: Inside the police station tonight, authorities telling us they've received dozens of tips, and doubled the reward to $40,000. We believe that he either is familiar with the area or he lives in the area, so, we're hopeful that someone in the area where the shooting occurred could lead us in the right direction. Reporter: Hunting for the toddler's killer and the black 2003 Chevy impala he was said to be driving. David, a candlelight vigil for little acen will be held behind me here tomorrow night. The community coming together where this tragedy occurred.
This transcript has been automatically generated and may not be 100% accurate.