The mother of a slain Philadelphia police officer and loved ones of two other fallen officers addressed the Democratic convention Thursday, calling for unity at a time of heightened tensions between law enforcement and civilians.

That tension was underscored this week by the Philadelphia police union's rebuke of the Clinton campaign for not initially scheduling speaking time for fallen officers' families - and by words heard in the Wells Fargo Center during a moment of silence just before they spoke.

In that silence, a few people shouted, "Black Lives Matter!"

Moses Walker, a 19-year veteran of the Philadelphia Police Department, was fatally shot on his way home from work in 2012. On Thursday night his mother recalled her son's loving spirit.

"Moses didn't live long enough to give all of the gifts he had to give," Wayne Walker told the thousands of delegates. "While we're here, we must do the good we can. Absolutely we have to believe that we're stronger together."

Walker's killer, Rafael Jones, was convicted of first-degree murder and other offenses and sentenced to life in prison without parole last year. He and an accomplice robbed Walker, 40, as the officer walked to a bus stop in North Philadelphia.

The accomplice pleaded guilty and testified against Jones in exchange for a lighter sentence.

Wayne Walker addressed the convention a week after the city police union said Democratic nominee Hillary Clinton should be "ashamed" for inviting family members of those killed by the police to speak without also inviting loved ones of fallen officers.

On Tuesday, following chants of "Black Lives Matter," black mothers addressed the convention, recalling their children who were killed by police or were victims of other gun violence.

John McNesby, president of Fraternal Order of Police Lodge 5, praised the decision by the Clinton campaign and convention organizers to add family members of fallen officers to the speaking lineup.

"We want fairness to both sides," McNesby said. "It seemed like we got the door slammed in our faces. I guess they listened, had a change of thought, change of heart."

Asked if he stood by his criticism of Clinton, he said: "Had the FOP not stepped up and said anything, there would absolutely be no survivors on that stage tonight."

The convention committee and the Clinton campaign did not respond to requests for comment.

Jennifer Loudon, widow of fallen Chicago police officer Thor Soderberg, said: "I know that in light of recent events, some of us have lost faith."

To applause, she said she wanted Americans to know of "all the officers out there who every day risk their lives protecting all of us."

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