Sharpton hugged Cecilia Reyes during an appearance Saturday at his Harlem headquarters. He said it's "unthinkable for a mother to have to bury her child."
Reyes' son Noel Polanco was shot Thursday after police pulled him over for a traffic violation near LaGuardia Airport.
The 22-year-old was unarmed.
Police have offered no explanation for why a detective fired after approaching the car.
Sharpton said that "for unarmed innocent people to be killed is wrong and it's got to stop."
Reyes called her son "a great kid." She said he had hoped to be placed on active duty in the Army and then join the Police Department.
Get Eyewitness News Delivered