Wayne Lipscomb, the mother of slain Philadelphia Police Officer Moses Walker, Jr., addressed the crowd.
The 19-year veteran was shot and killed during a robbery attempt in 2012.
"Moses didn't live long enough to give all of the gifts he had to give. While we're here we must do the good we can," Lipscomb said.
PHOTOS: The 2016 DNC in Philadelphia
Family members of other fallen officers also spoke, saying they never want those sacrifices to ever be forgotten.