Isaiah Rodriguez was in the passenger seat of a car when it was hit by another vehicle on Nov. 3 at the intersection of San Juan Avenue and Firestone Boulevard. His 19-year-old sister was hurt in the crash.
A woman who tried to help the young victims at the time of the crash spoke out at the vigil on Wednesday.
"We need justice for that little boy and for his sister and for his family. His mother is aching and hurting right now," said Carlene Juarez. "Christmas and Thanksgiving are coming up and she doesn't have her baby boy."
A GoFundMe account has been set up to help the family.
Investigators believe that speed may have been a factor in the crash. The off-duty deputy has not been identified. The incident is still being investigated by the South Gate Police Department.