Minneapolis police Monday appealed for anyone with knowledge that could solve the killing of 3-year-old Terrell Mayes to contact them, saying they're confident someone has the information they need to solve the case.

Police and the boy's mother, Marsha Mayes, said they're reminded daily of the murder four years ago Saturday.

"It is one of those cases that the people behind me take personally," Police Chief JaneƩ Harteau said at a news conference, her voice trembling slightly. "I keep Terrell's picture on my desk to remind me."

The case is being handled by a Cold Case Squad whose formation was announced by the department in September. Four investigators are assigned to the Mayes killing, the department said. There is a $60,000 reward for the person whose information solves the case. It is the sixth older case to be publicized on the department's website, www.insidempd.com.

Mayes was killed the day after Christmas in 2011 by a stray bullet that hit him as gunfire erupted nearby. He was struck while running up the stairway of his house on the 2600 block of Colfax Avenue N.

His mother said she thinks multiple people know what happened that day. But she attributed their failure to come forward to shame. "Who wants to tell me to my face that they killed my child?" she said.

She also said she feels a lack of support from the activists who have been marching since the death last month of 24-year-old Jamar Clark. He was shot by police during an altercation at an ambulance on Plymouth Avenue N., sparking protests over whether the shooting was justified.

"I have a little resentment and bitterness and anger for my community," she said, noting the absence of community pressure for the killer to come forward. "I see people marching for other stuff."

"Colfax knows what happened. Dupont knows what happened," she said, citing two blocks adjacent to the house were Terrell was shot. Mayes has since moved away from the block with her two older and two younger sons.

Asked if police think the shot originated on the block or farther away, Lt. Richard Zimmerman said the shooting was gang-related and, "It was near the house."

"We need somebody in the community to come forward with that one piece of information that we need," Commander Catherine Johnson said. "That's what's going to give our investigators the information they need."

The Cold Case Squad was established to review dozens of unsolved murders in concert with representatives of the Hennepin County attorney's office and the FBI, with whom detectives assigned to the squad meet monthly. They review what cases deserve a fresh look with more resources.

The first half-dozen cases publicized on the website range between 1989 and 2012. None of the cases publicized has gained a significant lead to date, according to department spokesman Scott Seroka.

Besides Mayes, the victims include Lois Swenson, found beaten to death in her North Side house in 2012; Joe Behrend, found beaten to death in his South Side apartment in 1989; Luis Figuero-Morales, found shot to death on Lake Street; Ali Yassin Ismael, found dead in a car at E. 19th Street and Nicollet Avenue S. in 2009; and Larry Powell, killed by a single shot and found in a North Side snowbank in 2009.