Castile, a black man, was shot several times after he was pulled over with Reynolds and her 4-year-old daughter in Falcon Heights on July 6.
He later died at the hospital.
"It's been going on too long," his mother, Valerie Castile, told reporters on Tuesday. "I used to look at TV and see other parents under these same circumstances and say, 'Wow, I hope that would never happen to me.' But it has."
She said her son would have turned 33 on July 16.
The two St. Anthony police officers involved in Castile's shooting have been placed on administrative leave.
The Minnesota Bureau of Criminal Apprehension has launched an independent investigation into the use of force in Castile's death.