When our country takes kids away from their mothers and fathers as punishment for coming to this country to seek asylum, when we call those kids “unaccompanied alien children” after we’ve forcibly “unaccompanied” them and sent them to shelters without any clear idea of when, or if, they’ll see their moms and dads again…we’d like to say this isn’t us, this isn’t what we do, this isn’t America.

Today, we did something about it. We took action.

With less than 24 hours notice, thousands of our fellow Americans made the trip to Tornillo — where a makeshift shelter of tents has been constructed to hold those children — to bear witness, to testify to our fellow Americans, and to force us to act.

Under a bright sky and a sun that burned our faces and the backs of our necks, we remembered that we were there for the families who’d traveled under these same skies — for thousands of miles — and endured under this same sun, arriving to this country burned, dehydrated and desperate. Like millions of families over the course of our history, they finally arrived, in the hope that they had found refuge, shelter and asylum when their own country could no longer protect them from hunger, brutality and death.

They came only to discover that under a new zero-tolerance policy, that those parents who had risked everything to bring their children here — as any parent, any human would do — as Amy and I would do in the same situation — would have their children taken from them.

So we marched to the Tornillo tent city that was constructed last week to house the children of those parents and the children who had arrived without parents. There are over 200 children in there right now. Up to 4,000 coming over the days and weeks ahead.

My 7-year-old son Henry called me to wish me a happy father’s day this morning before we left for the march. I told him I loved him and I’d see him soon but today we were marching to be there for those kids being detained in Tornillo. He asked me if Tornillo was a jail or if it was a camp. And I told him it’s kind of like both at the same time.

And then he asked me,

“Why, dad? Did they do something wrong?”

There’s no more important time to be alive than this one. To be an American, to be on the U.S.-Mexico border, to have the opportunity to define who we are as a country.

What’s happening right now, it’s on us, all of us — no person, no party, no administration however powerful. It’s on all of us, the people of America.

And after today I know that America is ready to meet this challenge, this test — a moment that will define us for the rest of our lives and for the history to be written long after we’re gone.

Whether it was Angela who came in from Rockport, a city still recovering from Hurricane Harvey. Or the delegations from Midland, Lubbock, Dallas, Austin and Houston. Joe, who took two flights from Boston. All the kids from El Paso, the teachers from Fort Hancock, the families from New Mexico. A woman who learned about this 20 hours ago in Salt Lake City, and jumped in the car stopping only for gas and a McDonald’s.

People from all walks of life. Musicians (thank you David Garza and Jim Ward!), teachers, veterans, retirees, activists and shut-ins. People who’ve never been involved in politics, people who hold public office, people who want to hold public office. And people who want to hold those in public office accountable.

Veronica Escobar, our former County Judge and future Congresswoman who initiated the call to action and brought us together. Lupe Valdez who for the day suspended her campaign for governor and flew to El Paso, got a few hours of sleep and then drove to Tornillo to help lead the march. Fernado Garcia. Ruben Garcia. Cristobal Joshua Alex. Melissa Lopez. Congressman Joe Kennedy.

Today we were able to bear witness, to ensure that this is on us, on our conscience. And that we bear that burden now because we know it will be unbearable for long — that it will force us to act, to push, to pressure, to ensure that our laws reflect our kids, those kids, and that idea and ideal of America that we still hold true.

No good tough important thing has ever happened in this country because Congress, Presidents, people in positions of power, woke up and decided to do the right thing. It’s only ever happened when the people of this country forced those who had the power to use it for our common good.

I saw that today, and I am grateful that I got to be part of it.

Editor’s Note: The main photo accompanying the above guest column shows U.S. Rep. Beto O’Rourke speaking at a rally against the Trump Administration’s “zero tolerance” immigration policy. The photo was taken outside “tent city” in Tornillo, Texas, by Ivan Pierre Aguirre for the Texas Tribune.