Six men who sold more than 70 weapons to undercover detectives in the same New York City area where a policeman was fatally shot last week have been arrested and indicted on conspiracy and gun charges, authorities announced Tuesday.

Most of the 74 weapons — from handguns to an assault rifle — were loaded when sold to undercovers in and around the Harlem area of upper Manhattan, including two near where Officer Randolph Holder was shot in the head on Oct. 20, officials said.

"We are having this conversation against a very, very painful backdrop," Mayor Bill de Blasio told reporters. "What adds to the pain of that loss is that these guns are so available and that it is a national problem."

The funeral for Holder, 33, a five-year NYPD veteran, is Wednesday. Hundreds of fellow officers attended his wake Tuesday.

Tyrone Howard, 30, was arrested and charged with murder and robbery. He was indicted by a grand jury on Tuesday. He hasn't entered a plea but his attorney has said there are many missing details in the case.

When Harold was killed, Howard was free on bail but wanted for skipping court after a state Supreme Court judge referred him to a diversion program instead of prison in a drug case.

That same judge, Edward McLaughlin, was to hear the arraignments of the men indicted in the gun sting announced Tuesday.

Manhattan District Attorney Cyrus R. Vance Jr. said his confidence in McLaughlin's decision-making wasn't shaken. He added that judges should have so-called risk assessment tools designed to measure a defendant's dangerousness when determining bail conditions.

McLaughlin is "as concerned about public safety in the city of New York as any judge I've seen," Vance said.

Investigators will trace where the guns, for which undercover detectives spent more than $52,000, were originally obtained, officials said. But they likely originated from sellers in southern states such as Georgia and Virginia that regularly supply firearms traffickers in New York, frustrating law enforcement, Police Commissioner William Bratton said.

The .40-caliber Glock handgun authorities believe was used to kill Harold was originally obtained in South Carolina, officials said.