Longtime NYPD critic Al Sharpton on Saturday laid a memorial wreath for a slain police officer -- days after the cop's grieving sister questioned Sharpton's whereabouts.

"R.I.P. OFFICER HOLDER FROM NATIONAL ACTION NETWORK," said a bow draped across the floral arrangement Sharpton placed outside Police Service Area 5, home to the housing bureau unit of Randolph Holder, 33. Holder was shot in the head Tuesday evening in East Harlem, allegedly by a gunman he was chasing.

Earlier in the morning, preaching as he does weekly at his Harlem storefront headquarters, Sharpton said he was just as determined to "take out the demons" on the police force who abuse their power as he was to excise "the demons that shoot policemen."

"I am concerned when I see a good policeman harmed, shot in cold blood," he said. "And the community he protected and served ought to stand up and let his family know that his life had value to us."

He added: "Right is right and wrong is wrong."

At the initial court appearance Wednesday by the suspected shooter, Tyrone Howard, 30, Holder's sister Sherry Holder bellowed to ask, rhetorically, where Sharpton was.

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His organization soon issued a statement noting that he had tweeted condolences hours after the shooting and was attempting to visit with the Holder family. On Saturday he noted he had also placed a wreath to remember two cops slain last year in Bedford-Stuyvesant, Brooklyn.

At Sharpton's side at the police building on East 123rd Street Saturday was Gwen Carr, mother of Eric Garner, the Staten Islander whose death by police during an arrest for illegal cigarette peddling catalyzed months of protests, many led by Sharpton.

Carr said she wanted to show support for Holder's bereaved family.

"He has a family," she said, as two police union delegates loomed. "They're hurting."

She added: "All police are not bad. But the ones that are, we need to get rid of them. And just like the criminals that's out there in the street, we need to get rid of them, you know?"

Sharpton's followers had traveled to the police building for the wreath laying in a yellow school bus the activist preacher chartered. As dozens filed out of his headquarters to board, a table offered handouts, such as for a "STOP POLICE TERROR & MURDER" march happening simultaneously in Washington Square Park.

Asked the ad: "Which side are you on?"