The Grateful Dead concert at Soldier Field on July 4. View Full Caption DNAinfo/Mark Konkol

When the Grateful Dead opened their Fourth of July show with one of my favorite tunes, I couldn’t help but think of our divided city.

“Shakedown Street” a musical tale of the hidden vitality — lingering remnants of joy — you can find even in the most downtrodden parts of town if you dare to look.

“Nothin’ shakin’ on Shakedown Street. Used to be the heart of town,” we all sang along. “Don’t tell me this town ain’t got no heart. You just gotta poke around.”

In the hours leading up to that moment, I encountered a series of random acts of kindness with friendly strangers while meandering through the parkland and parking lots surrounding Soldier Field — the southernmost gateway to the best of Chicago.

At the souvenir stand, a cute couple from Bakersfield, Calif., braved the merch table to order me a poster I had my eye on, sparing their new Chicago pal the gentle crush of the patchouli-scented crowd.

In the late afternoon sun atop the parking deck, a computer genius offered two wondering strangers a couple cold ones — and intriguing chat — for no reason at all.

And at any moment, if you desired a high-five or a gentle hug from a stranger it was yours — no questions, no funny looks.

Sure there were a few bad apples who found their way into cuffs. Police arrested one person for marijuana possession, two people for drinking on the public way, four people for possession of a controlled substance, six people for trespassing.

But overall, the mass of pot-smoking, tie-dye T-shirt wearing Deadheads who descended on Chicago brought with them a positive vibe powerful enough to distract me from the harsh truth of what Independence Day has become in forgotten parts of our town — a holiday weekend blood bath.

The Grateful Dead’s jam-band distraction lasted only as long the band played, the long strange Metra trip home, some sweet dreams and, for a few lucky pals, a final Grateful Dead farewell show at Soldier Field.

By Monday, reality had set in, again.

Over the holiday weekend in parts of Chicago out-of-town hippies probably didn’t visit, more than 48 people were shot and wounded, seven fatally — that’s just during a 54-hour stretch reported by police.

In all, that is two fewer shooting victims than the July 4 holiday weekend last year, police said.

Somewhere, there’s probably a city bureaucrat who silently believes that’s a minor victory for our police department, but it’s not.

What people should see in those easy-to-compare police shooting statistics that make such sensational headlines is that it’s time to stop measuring the effectiveness of our police department solely by increase or decrease in shootings compared to previous years.

And the only way to make Chicago a safer place to live is to catch and convict the shooters who terrorize the parts of Chicago that visitors — and wealthy natives who know better — fear to tread.

But that isn’t happening in Chicago.

It’s common knowledge on the street that even if you shoot-and-injure someone, there’s an excellent chance you’ll avoid jail — and get the chance to shoot again.

Consider this: In 2012, gunmen who shot and wounded someone got away without criminal charges 94 percent of the time.

And that was even worse than the 91.5 percent of shooters who escaped charges in 2011, according to a DNAinfo.com analysis of police data.

Why stop shooting if there’s only a 6 percent chance of getting caught?

It’s no secret the No. 1 reason shooters don’t get charged, convicted and sent away to prison is the ridiculous, cowardly and pervasive “no-snitch” code of silence on the street.

This bloody weekend reminds us of that, again.

Just before midnight Saturday, a stray bullet meant for an alleged high-ranking gang member, Antonio Brown, struck and killed the man’s son, 7-year-old Amari Brown, near Humboldt Park, police say.

And Antonio Brown — who has been arrested 45 times for crimes ranging from gun possession to burglary — has refused to cooperate with police to help catch his own son’s killer, Police Supt. Garry McCarthy said.

Let me repeat: A man won’t cooperate with police even to catch his own son’s killer.

That’s the no-snitch culture — a shoot ‘em up Bizarro World where some people revere silence and street vengeance above all else — that exists in the part of Chicago that people increasingly refer to as “Chiraq.”

The rough neighborhood where little Amari was murdered and the glorious lakefront stage where the Grateful Dead played a musical farewell to fans are only eight miles apart.

But they might as well be two totally different worlds.

After Sunday’s show at Soldier Field — in the heart of glimmering, wealthy Chicago — Grateful Dead percussionist Mickey Hart offered fans some great advice before saying goodbye.

“The feeling we have here — remember it, take it home and do some good with it,” he said. ”I’ll leave you with this: Please, be kind.”

Under much different circumstances, there’s a universal truth in that message — one that I hope reaches someone who witnessed a shooting this weekend in the forsaken parts of Chicago overwhelmed by so much violence, poverty, desperation and fear.

Because that feeling you have after seeing an innocent child get shot and killed right before your eyes — you should remember it, take it home with you and let it inspire you to do the right thing.

I’ll leave you with this: Please, speak up.

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