I'm always amazed after someone has done something horrible, how often those who knew that person were so surprised.

Take shooter Charles Carl Roberts in Pennsylvania — to all who met him and knew him, he was quiet and unassuming. A family man, a decent man. Then... a murderer.

Or Congressman Mark Foley. A family man, a good man. But now, by all accounts, a very sick and troubled man.

Time and again those we thought we knew, we find out we didn't... and don't know at all.

If I've heard it once, I've heard it a thousand times — after these shooting stories, in particular:

"He was such a nice guy."

"A quiet guy."

"Never caused much trouble."

Then after the damage, comes the dig... into e-mails which should have tipped us, family arguments that might have scared us.

Maybe we all missed the signs. Maybe, in the case of Washington, we just ignored them.

I don't know. This much I do know: What you see in a person isn't necessarily what you get in that person.

Nothing profound here, I guess, just a message for our times here.

We live in a world where appearances count for a lot. Many spend a lifetime crafting them. Then, in a single incident on a single day, destroying them.

We are shocked. We are stunned. And we are left wondering: How could we have been so wrong? I don't know what's more troubling. The fact we ask that question. Or the sadder fact, we can't answer it.

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Neil Cavuto serves as senior vice president, anchor and managing editor for both FOX News Channel (FNC) and FOX Business Network (FBN). He is anchor of FNC's Your World with Cavuto - the number one rated cable news program for the 4 p.m. timeslot - as well as the FNC Saturday show Cavuto on Business. He also hosts Cavuto on FBN weeknights at 8 p.m. In addition to anchoring daily programs and breaking news specials on FNC and FBN, Cavuto oversees business news content for both networks and FNC's weekend business shows, including Bulls & Bears, Forbes on Fox, and Cashin' In. Click here for more on Neil Cavuto.