Rep. Mike McCaul: Intelligence Key to Preventing Train Terrorism

House Homeland Security Chairman Michael McCaul said Monday that he's always been worried about train security, but after the thwarted terror attack on a French train over the weekend, he's more concerned than ever.

"Right now, we have the canines that are out there, we have, you know, the officers," the Texas Republican told MSNBC's "Andrea Mitchell Reports" program on Monday.

"But I also think intelligence is really the key to preventing this."

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Meanwhile, in the case in France, there were "warning flags that went up on" the alleged attacker, 25-year-old Ayoub El Khazzani, who boarded the high-speed train in Brussels and headed to Paris armed with a Kalashnikov assault rifle, a Luger automatic pistol, ammunition and a box-cutter.

"My concern was his travel from Europe to Istanbul and then into Syria and then flying back into Europe," said McCaul. "I think that's the biggest vulnerability gap that they face."

McCaul said the United States works with overseas transportation systems, but "the fact is that they're still very wide open."

"There's a big security gap in terms of vetting Europeans past any watch list when they fly out of the region from Istanbul into Europe," said McCaul, who noted he visited Istanbul recently.

"There were really two flags that were missed. One when he flew out of Istanbul and then back in. It's unfortunate. The good news is we had American heroes that stopped it."

McCaul, being from Texas, also noted that there is a lot of talk about operational control when it comes to border security and having a better understanding about who is crossing the border.

"I know there's a lot of discussion about building a 2,000-mile wall," he said. "I think we need to complete the Secure Fencing Act but we need greater technology and aviation aspects down on the southwest border so we can see the threat from the sky."

Until the threat is seen, he continued, "you don't know where it's coming from and how to correctly stop it."

A bill that McCaul passed out of his committee recently deals directly "in terms of allocation and more aviation and technology assets down to the border."

But a fence is a "barricade, but it's not a panacea," he said. "I won't solve the problem completely. You need the technology and aviation aspects to counter that."

And as for Donald Trump's talk of a fence?

"I think there's kind of a simplistic, kind of knee-jerk response that all you have to do is build a 2,000-mile wall and the problem is solved," said McCaul.

"Anybody who's been down to the borders, it's not that simple. When I look at the fencing down there, it will stop them temporarily. They'll dig under it. Go over the fence. I think the fencing is important, but I think it is more important is to have the aviation assets from the sky and also be able to respond to it."

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