I still don’t understand quite how it happened.

He was standing on the curb, carefully waiting to cross until the avenue was unmistakably empty.

I was watching from my car, since I had never let him cross this street by himself. This narrow but busy street.

But today he wanted to do it himself. He scoffed at my knee-jerk protests, my smothering mothering, assuring me with his eyebrows and exasperated grin that jeez, he was almost nine, he’d done this with me a thousand times before and he could certainly navigate a straight, brightly lit, 20-foot crosswalk on his own. (The kid can say a lot with his eyebrows, trust me.)

But then there it was. Before I even knew what was happening. The careless bounding from the curb, the squeal of skidding tires and my son’s fear-frozen body silhouetted against the grill of the white pick-up truck that was suddenly upon him.

Every cubic millimeter of air in my lungs rushed out of my throat in a guttural scream, and when I realized that wasn’t going to be enough to stop this horror movie, I covered my eyes with my hands — which, looking back, seems like a self-indulgent thing to do.

When I uncovered them, I saw my son standing upright and ashen-faced amidst a cloud of white smoke. The truck had fishtailed sideways. The smell of burnt rubber was strong.

He bolted back to my car, leaped inside, and we both sat staring in terror out the windshield until one of us could speak.

“I don’t know what to feel,” he said, and burst into tears.

I knew exactly what to feel. Powerless. I have never felt so utterly useless in my whole life. If a boy’s own mother can’t keep him alive, forchrissake, who can?

We didn’t get to meet the truck’s driver before he drove away. I wanted to thank him — hell, to kiss him — for not being on his cell phone, or being drunk, or even fiddling with his radio when my son darted in front of him. (And if you’re reading this, sir, please know that you will always be the example our family uses to define the word “hero.”)

So we just sat together, hugging, sniffling, jittery with lingering adrenaline and trying to convince ourselves it hadn’t been as ugly as it seemed. Surely the truck hadn’t been as close as we thought. And look, we’re both sitting here now. We’re both fine. Everything’s really very fine.

But in truth, we both knew how close we had come to life-snuffing tragedy. It was about five feet.

That evening, as I bid my son goodnight, he asked me to leave his bedroom door ajar. It’s a frequent request; he likes the comforting, sleep-inducing clickety-clack of my keyboard as I work at my computer downstairs. But tonight he mumbled something I didn’t expect.

“Mom?” I heard him say. “Are you gonna protect me?”

And I went cold. Because clearly, as I’d demonstrated today, the answer was no. No, my precious treasure of a boy. No, I guess I’m not. I guess I can’t.

“What?” I asked, looking for a clue on how to answer, how much assurance he needed in order to sleep serenely and not re-live the moment over and over in his dreams the way I knew I would tonight. And tomorrow night.

But when he repeated himself, I realized I had misheard him.

“Are you gonna be typing?” he said again, with an easy yawn.

The question hadn’t been an accusation, but an affirmation. Proof that while I may not always be able to keep him safe, when life sends trauma skidding and screeching to his feet, I can at least bring him some peace.

And maybe that’s the best a parent can do.