People embrace in front of a memorial outside the Tree of Life Synagogue in Pittsburgh on Sunday. (Brendan Smialowski/AFP/Getty Images)

Jeff Blattner, a member of the University of Colorado Law School’s adjunct faculty, is president of Legal Policy Solutions and a board member of HIAS.

The horrific shooting at Tree of Life Synagogue in Pittsburgh happened on the eve of the anniversary of my own bar mitzvah there, some 51 years ago. Pittsburgh’s Jewish community was then, and remains today, a giant family. Even those of us who moved away have stayed closely connected to it and to each other. Our hearts ache as one.

The synagogue is at the heart of the close-knit Jewish community in Squirrel Hill, a bustling neighborhood filled with tree-lined streets and ethnic restaurants. Pittsburgh is a city where neighborhoods like this are still common, where people get to know one another, where they welcome new neighbors and mourn the passing of old ones. It is a city of grit and compassion, one that can offer a model of how to counter the hatred that is tearing America apart.

The suspect in the 11 synagogue murders was reportedly motivated by anti-Semitism and anti-immigrant hatred. A particular target of his venom, according to news reports about his apparent online posts, was the Hebrew Immigrant Aid Society, or HIAS, an organization that assists refugees of all faiths. I am proud to serve on its board.

An appreciation for how immigrants enhance America was instilled in me by my parents and grandparents, all of whom were refugees from Nazi Germany welcomed by my hometown. The Pittsburgh of my youth was not a melting pot; it was a rich ethnic stew of Italians, Irish, Slavs, Poles, Scots, African Americans, Lebanese and Jews, among many others. We didn’t always get along, but we saw ourselves as members of one community — one “tahn” as we Pittsburghers say.

On Sundays, we worshipped together at the altar of the Pittsburgh Steelers, whose stadium was adorned with banners proclaiming “Franco’s Italian Army” (National Football League Hall of Fame running back Franco Harris was born to an African American father and Italian mother) and “Dobre Shunka,” the Polish “Good Ham” nickname of another Hall of Famer, linebacker Jack Ham. Sports commentator Howard Cosell once said, “When you play Pittsburgh, you play the whole city.” The Pirates’ theme song during its World Series-winning 1979 season: Sister Sledge’s “We Are Family.” We were all on the same team.

That strong sense of community was tested in the 1980s, when Pittsburgh struggled with the collapse of the steel industry. But the city gradually recovered, thanks to enlightened leadership, top educational and medical institutions, and an economy fueled by high-tech jobs in robotics, artificial intelligence and health care. But not too far from areas with trendy new restaurants and bars, some of those former steelworkers and their sons and daughters still struggle with unemployment, and with the resulting despair that feeds addiction, anger and alienation. Pittsburgh’s mayor, Bill Peduto, appears to be working hard and creatively to extend Pittsburgh’s new prosperity to all its inhabitants and to help those who might otherwise be left behind. America needs more of that.

I fear we’ve gotten away from seeing all Americans as “us” — from seeing all Americans’ problems as worthy of our attention. Today we’re Red States and Blue States, flyover America and coastal elites. There are many reasons. Most important, cynical politicians and self-interested plutocrats have sought to foment hatred, division and resentment. The public sphere is being poisoned, and now people have been killed in the town I love. Those who stir hatred and exploit it must be condemned, and they must be defeated.

At that same time, though, all of us who regard some portion of the nation as “them” must change how we think. If we are to have no more Tree of Life massacres — I can’t believe that phrase now exists — Americans need to think of one other as part of “us.” Like Pittsburghers, when we see someone in our communities who doesn’t look like us or think like us or pray like us, we still need to think: “us.” We need to find ways to make all of us better off — respecting differences and seeking compromise. Pittsburgh has lots of institutions that support that broader sense of shared community. We must find ways — through community service, civic education and forward-looking leadership — to support similar institutions across the country.

In 1968, Robert F. Kennedy went to Appalachian Kentucky to focus public attention on the plight of the white working poor. He made similar trips to highlight the plight of African Americans in rural Mississippi and Latinos in California. To RFK, all of their problems were “our” problems, and so it should be today. The problems of rural America and urban America, coastal America and middle America, Red America and Blue America, are all our problems.

If we don’t commit ourselves to solving them together — to seeing one another as part of a bigger “us” — we may reap a whirlwind of ever-widening division. Let Pittsburgh, in its grief, show us the way.