LISA ESPINOSA'S youngest son, Raymond Pantoja, was killed April 10 outside a nightclub at B Street and Allegheny Avenue in Kensington.

The 26-year-old father was shot after an altercation in front of a crowd of people, including some friends - though I use that word loosely. Friends don't watch friends get gunned down and say nothing.

Hell, humanity should dictate that even strangers wouldn't watch someone get shot and go on about their lives. But often that's exactly what happens: men, women and children gunned down in broad daylight, in front of plenty of clear-eyed witnesses who don't say a word.

In Philadelphia.

In Chicago.

Even in Chester. Recently, my colleagues Caitlin McCabe and Grace Toohey wrote about how people are getting away with murder there. Despite the highest homicide rate of any city in America, only a third of the killings in Chester get solved. And that includes the slaying six years ago of a 2-year-old who police said was killed by bullets meant for his father. The father refused to cooperate.

In Philadelphia, 131 of the 194 homicides as of Sept. 12 were unsolved.

Do the math, and I'm not just talking about the subtraction that yields a dismal 63 solved murders this year.

I'm talking about loss compounded by a lack of answers, of justice. By loved ones unable to truly mourn and residents left increasingly more vulnerable as killers go free.

Espinosa certainly hasn't been able to mourn her son. She'd have to stop moving long enough to do so, and she won't stop until her son's killer is arrested.

"It's not just for my son," she said. "There are cold-blooded killers roaming around our communities every time people stay quiet."

Some of the people outside the Kensington club the night her son was killed pointed their cameras at the altercation between Pantoja and another man that preceded the shooting. The cameras rolled after another man pressed a gun into Pantoja's chest and fired, but his identity was hidden by a hoodie.

Police need help. Espinosa needs help.

Espinosa tracked down the guys who were with her son the night he was killed and urged them to come forward. She tried to appeal to their consciences, and when they revealed they didn't have them - they told her there's a street code, and they wouldn't snitch - she took matters into her own hands.

She pored over social media sites for any information she could pass on to detectives working her son's case.

She turned a room in her apartment into a makeshift headquarters for spreading the word about her son's murder, including fliers and huge photos with information about the $20,000 reward for information that leads to an arrest and conviction and the anonymous Citizens' Crime Commission tip line at 215-546-TIPS.

Last week, Espinosa organized a kickoff event for the National Day of Remembrance for Murder Victims, designated by Congress for Sept. 25.

She's working with politicians, activists and fellow grieving families to get more murders solved.

In another recent story about Philadelphia's rising homicide rate, my colleague Chris Palmer reported that while that rate has been rising, the rate at which police have solved those killings - the clearance rate - has been declining. Through July of this year, the rate was 54 percent.

We've seen this before, deferred grief transformed into relentless activism. It's what motivates Espinosa and so many others who tirelessly try to spread awareness of the impact of gun violence.

They are an inspiration, but the situation should shame us all.

The impact of violence is all around us.

On the faces of an ever-growing number of our neighbors.

On our streets.

In our emergency rooms and living room and classrooms - and even in our pockets, if any of that isn't enough.

At a marathon meeting about youth gun violence in March, Kathleen Reeves, the senior associate dean for health equity, diversity and inclusion at the Katz School of Medicine at Temple University, testified that the overall cost of gun violence in the United States in 2012 was $229 billion - about $90 million more than the budget for the U.S. Department of Education.

The only thing more glaring than the impact of violence is the silence that enables it.


On Twitter: @NotesFromHel : Helen.Ubinas