(CNN) -- A manhunt is underway in Little Rock, Arkansas, after a 3-year-old boy on a shopping trip with his grandmother was shot and killed during an apparent road rage incident, police said.
A motorist behind the woman Saturday evening grew agitated that she was not moving quickly enough, Little Rock Police Department spokesman Lt. Steven McClanahan said.
The man started honking his horn. He got out of his car and fired shots inside the woman's car, police said.
Police told CNN at least one of the bullets hit the boy.
Officers believe the incident occurred on the city's southwest side. The grandmother was at a stop sign at Mabelvale Cut Off Road and Warren Drive when a confrontation ensued, police said.
The woman later drove to a JC Penney in west Little Rock, where police received a call shortly before 6:30 p.m. that a child passenger had been shot.
The boy was transported to Arkansas Children's Hospital, where he was pronounced dead. A 1-year-old child was also in the car at the time of the shooting, according to a police report.
Police said the grandmother and the slain boy had no relationship with the suspect.
"I certainly have no information to say that anyone in this family has done anything to cause this young person's life," Little Rock Police Department Chief Kenton Buckner told CNN affiliate KARK. "But this is about as frustrating as you can be as a public safety official or just a plain citizen."
No arrests have been made yet. Crime Stoppers is offering a $20,000 reward for information leading to an arrest and conviction, Little Rock police tweeted Sunday.
Homicide detectives are conducting an investigation.
The fatal shooting marks Little Rock's 40th homicide of the year, police said on Twitter.
CNN's Andreas Preuss and Carma Hassan contributed to this report.
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