Beginning in 1880 — before the words “Give me your tired, your poor/Your huddled masses yearning to breathe free” were stamped on the Statue of Liberty dedicated 132 years ago — Jewish refugees fleeing violent pogroms in Europe were often met in New York Harbor by volunteers from the city’s teeming immigrant community.

“Jewish people going down to the docks, meeting the boats coming from Ellis Island, providing kosher meals, helping people reunite with their family members and get jobs” is how Melanie Nezer described the early years of what started as the Hebrew Immigrant Aid Society and is today simply known as HIAS. “That’s what we do today — the only thing that’s changed is that the people that we’re helping aren’t necessarily Jewish.”

In 2018, the world has more refugees than any time in its history, and wherever people are fleeing misery and seeking safe harbor — from war-torn Syria to America’s southern border, where a wave of migrants are trying to escape murder and deprivation — HIAS is probably there, offering legal aid, temporary shelter, or advocating for the plight of the displaced. The truth is that not too many Americans were paying much attention to the good work HIAS is doing.

And one of the few who did was a 46-year-old loner in his Pittsburgh apartment — the kind of man who said very little to his actual neighbors but had quite a lot to say in a cyber world of rank racial and religious hatred and white male supremacy that has been hiding in plain site.

The man who would become the alleged perpetrator of the deadliest attack specifically targeting Jews in the 242-year history of the United States had clearly harbored irrational anti-Semitic rage for some time. His hatred seems to precede the recent despicable downturn in America’s political discourse. The future gunman had a beef with President Trump, but it was that Trump was somehow too moderate, a tool of a bogus international Jewish conspiracy that he fantasized was everywhere.

Although HIAS — which has provided lawyers and other support for asylum-seekers on the U.S. southern border — has nothing to do with the caravan, the angry Pittsburgher blamed them nonetheless.

At 9:45 a.m., police say, he burst into the Tree of Life synagogue. Within moments, 11 worshippers lay dead and several more people were wounded, including police who raced toward the bullets and prevented an even more unimaginable catastrophe. One of the dead was a 97-year-old woman — old enough to be alive during the Holocaust — only to be murdered amid the hatreds of 21st-century America.

The synagogue shooting put an exclamation point on one of the worst weeks any of us can remember. It knocked out of the headlines several days of breathless news reports about the 56-year-old “lost soul” in South Florida who found a purpose and arguably a father figure in Donald Trump, and then terrorized Trump’s enemies in the media and in Democratic politics with (thankfully, ineffective) pipe bombs. Forgotten almost completely was the tale of an unhinged Kentucky man who reportedly tried to shoot up an African American church in Louisville and — thwarted by a locked door — went to Kroger and murdered the first two black shoppers he saw.

The last time Americans felt such despair bordering on hopelessness came exactly 50 years ago, when 1968 was shattered by the gunshots that killed Dr. Martin Luther King Jr. and Robert F. Kennedy and the riots in the streets.

This time feels the same and yet the circumstances are also very different. The dead are innocent everyday Americans who were merely trying to pray or buy groceries, the killers are avatars of a lost generation of middle-aged white men, and they are enabled by hateful rhetoric that comes from the very top.

Where to find hope? Many were quick to point out that Saturday’s synagogue shooting occurred just three blocks from the longtime home of one of Pittsburgh’s most famous residents, the late children’s TV icon Fred Rogers. “What changes the world?” Mr. Rogers asked once. “The only thing that ever really changes the world is when somebody gets the idea that love can abound and be shared.” It was also Rogers who told children that, in times of trouble, look for the helpers.

In Pittsburgh, one very bad man was consumed by his hatreds, but the helpers were everywhere. It starts with the remarkable courage of the police officers — from a department that still bears the scars from a 2009 incident when a right-wing zealot named Richard Poplawski gunned down three cops — who heard the gunfire and raced toward it. It also includes the thousands who took to the streets of Squirrel Hill to demonstrate the power of love.

Indeed. The only known antidote to hate is love. The only real way to fight back against Saturday’s insanity in Mr. Rogers’ neighborhood is to look for the helpers — and give them our support.

A version of this column first appeared in The Philadelphia Inquirer.