D.C. police use YouTube to post surveillance videos showing robbers at work, hoping to capture the public’s attention and a crook at the same time.

Now, detectives are using the same medium to seek help in unsolved killings investigated by the Cold Case Squad, and in other types of cases. The videos, posted for the first time Friday, include interviews with family members pleading for help.

The initiative goes beyond issuing news releases hoping a newspaper or television station will do a story, putting a detective in the role of producer and reporter.

“The community plays an important role in our efforts to reduce crime and close cases,” D.C. Police Chief Cathy L. Lanier said in a statement. “When members of the community come to us with vital information, they know we will act upon that information.”

Here is one of the videos:

Each video is up to four minutes long, and contains background music and close-ups of case files, the homicide office and the streets. One shows a detective paging through notes and includes a tight shot of an urn containing the ashes of man on a table in front of his grieving mother.

The police videos do not go into detail about the crimes or the circumstances.

Police are featuring three cases in their video release (the links take you to each video).

●The May 2006 shooting death of 35-year-old Marcus Johnson, killed in the 1400 block of First Street NW.

The victim’s mother, Mildred Johnson, pleads for help and talks about her son as the best football player among himself and his two brothers, but “his life went in a different direction” than a sibling who played pro football.

“I miss him so much,” Johnson says, adding later, “Please come forward and help me find Justice for Marcus.” She said she can’t accept his death until someone is held responsible.

● In an interview with WRC-TV Channel 4 in May 2011, Johnson said her son had been visiting his aunt and heard gunshots She said he went outside to protect children on the street and got struck nine times. In that interview, Johnson admitted that her son had sold drugs as a teenager but said he was trying to put his life together and had a steady job at a hospital when he was killed.

●The April 2008 shooting of 30-year-old Melvin Seals, killed in the 1200 block of Morse Street NE.

Seals was one of nine people killed in a bloody month on District streets. The Post’s Keith L. Alexander described the killing this way:

“Police were patrolling just a block away when Seals was shot at 2 a.m. at Morse Street and Montello Avenue, in front of a community center. He was hit 17 times. He recently had graduated from a city program that led to a position with the city’s Public Works Department.”

In the video, Seals’s mother, Deborah Seals-Craven, said her son had a child of his own, who still asks, “Where is my dad? Who killed my dad?” Seals-Craven said she wants to tell the gunman: “You haven’t lived a life. Why are you so mad and who are you mad at?”

●The Oct. 2010 disappearance of 24-year-old Unique Harris, who was last seen in the 2400 block of Hartford Street SE.

Harris was featured in The Washington Post’s Style section in October 2011 in a piece titled, “A young mother, gone without a trace.” In the video, the woman’s mother, Valencia Harris, pleads for help. “No family deserves to go through this,” she says.

Anyone with information on any of these cases is urged to call D.C. police at 202-727-9099 or text the department’s tip line at 50411. People with information that leads to an arrest and a conviction are eligible for a $25,000 reward.