"I'll take you to the police station and allow no harm to come to you," Pastor Terrance Long told ABC News. "We just want justice to be served."
The shooting happened Saturday while the 3-year-old was in the car with his grandmother and his 1-year-old sibling, Lt. Steven McClanahan of the Little Rock Police Department said Sunday.
When the grandmother, identified by police as Kim King-Macon, stopped at an intersection, a man in the car behind her honked, police said.
King-Macon honked back, and the suspect got out of his car and fired a gun, according to police.
The grandmother did not immediately realize the her grandson was shot and drove away, police said. She then pulled over and realized the boy was injured, after which she called police.
The boy was taken to Arkansas Children's Hospital where he died, police said. His sibling was not injured.
The pastor, who is organizing a Wednesday night vigil for King, told ABC News on Tuesday the family is "distraught."
Long said the last time he saw the boy was at a local restaurant; he said King was running around, jumping, and his grandmother told him to slow down.
Police called the shooting a road-rage incident and said the grandmother was innocent. They also said she had no relationship to the suspect.
McClanahan said today that police have interviewed the grandmother and believe she is telling the truth.
No arrests have been made, McClanahan said today.
Local and federal authorities have offered a combined $40,000 reward for information leading to the arrest and conviction of the suspect.
ABC News' Phillip Mena and Rob Hess contributed to this report.