Late one evening in April, a young couple was slain while sitting in a parked car in Minneapolis' Longfellow neighborhood. On June 1, Nehemiah Steverson, a popular Edison High School student, was found shot dead on a grassy patch on Newton Avenue North. Two months later, at least one gunman opened fire inside a crowded downtown nightclub, wounding nine people, one of whom later died.

These three homicides, and at least eight others this year, share a common thread: The killers remain at large.

Minneapolis police have solved about 60 percent of the city's homicides in 2014. While the number of murders in Minneapolis has fallen to near-historic lows, the percentage of homicides that go unsolved has remained fairly consistent. Left behind are parents, friends and loved ones consumed with wrenching loss, demanding justice and with lingering questions as to whether police are doing enough.

"We do have challenges with closing some of our cases," police spokesman John Elder said. "We know there are witnesses out there that hold the answers to some of our homicides, yet they refuse to speak up."

There were 36 homicides in Minneapolis last year, and a little more than half were solved, according to police statistics. So far in 2014, there have been 29 homicides, with arrests having been made in 18 of those cases.

Minneapolis police have had to deal with these unsolved crimes as they have worked to rebuild a depleted force hit hard by a wave of retirements. They have also tried to recruit more minority officers to help connect with communities of color, where some residents complain that the police are not as engaged.

Marsha Mayes said she has been frustrated by the police investigation into the death of her 3-year-old son, Terrell, who was killed by an errant bullet that tore through their north Minneapolis home on the day after Christmas, three years ago. No one has been charged with his murder, even after authorities offered a $60,000 reward for any information on the shooting.

Mayes said as the months wore on after her son's death, she stopped hearing from detectives.

"I just basically come out and look for my son's killer," Mayes said.

Police officials said they are aggressively pursuing every lead but declined to share details about any ongoing investigations. Doing so, they said, could tip off suspects and frighten away people who might have information about the case. Releasing certain information could tip off a suspect as to who might be talking with police.

"If we have witnesses providing information, we don't want to taint those witness statements by releasing information to the media that may not already be out there," said Cmdr. Catherine Johnson, who runs the department's Violent Crime Division.

Police also don't want to do anything to disturb their search for people who might have information but were not directly involved.

"If we have situations where we might be looking for identifications of individuals, we don't want to put out there who those individuals might be," Johnson said.

While the lockdown on information can be maddening for friends and family of victims, it has proved successful.

Earlier this year, police say they arrested Manuel Guzman using similar techniques. Guzman was charged with fatally shooting Rufino Alejandro Clara-Rendon after accusing him of being a police informant. After shooting Clara-Rendon, Guzman burned the body, according to court records.

More cases are still quietly being investigated.

On Sept. 16, a young man was fatally shot while fleeing his attackers outside his aunt's house on a block in north Minneapolis' Jordan neighborhood.

A month and a half later, Jemario Langston's murder remains unsolved and authorities have released few details on the shooting.

On the day of his shooting, rumors about who may have killed the 18-year-old and why swirled through the neighborhood, outside the earshot of homicide detectives. Some speculated that he had been killed in retaliation for an earlier incident. Others blamed his death on a flood of unchecked gang violence that had marked the past few months in the neighborhood.

Cindy Kennedy said that living in a neighborhood often rocked by crime and violence, they have come to feel a disconnect between the police and some of the communities they serve.

Kennedy's son, Quantell Braxton, 14, was gunned down more than three years ago while walking to a sleepover at a friend's house near North Commons Park. She said that detectives stopped returning her phone calls a month after the shooting.

"It gets to the point where I have to e-mail them before I can get a response," she said on a recent afternoon. "It's really frustrating. I'm trying to understand what is so difficult for them to say, 'Hello Cindy, we don't have any information to give you, because we don't have any.' "

"I'd be happy with that," she said.

Police officials insisted they are not giving up on any open murder investigation. Police say the investigations are often hampered by the reluctance of witnesses and victims to come forward for fear of retribution if they are seen as helping police.

The most high-profile open case in recent months was the Aug. 8 shooting inside 400 Soundbar, in which at least one gunman opened in the now-closed nightclub, wounding nine people. One of the victims, believed to be the intended victim, died a month later of his injuries.

Police have released few details about their investigation. So far, no one has been charged in the incident, one of the worst mass shootings in the city's history.

Several victims' families said they understand police frustration over the reluctance of witnesses to come forward but were equally frustrated by detectives' unresponsiveness.

Several, like Kennedy, have spent months, even years, looking for the killers on their own. They have spent their own money to pass out fliers and chase rumors.

Kennedy said it is painful to wake up and not see her son.

"Not be able to watch him become a grown man, make a family of his own, go off to college," she said. "Not be able to see him on his 15th birthday, not being able to see him go to prom."

She paused to catch her breath: "It hurts so bad."

Libor Jany • 612-673-4064 Twitter:@StribJany