MANCHESTER, N.H.

Donald Trump responded to the worst mass shooting in American history in a way that was a perfect X-ray into his character. He congratulated himself, via Twitter, for his supposed prescience in predicting more terror. He demanded that President Obama and Hillary Clinton call this outrage “radical Islamic terrorism,’’ as though those words have a talismanic, carnage-ending magic. He suggested that perhaps President Obama didn’t actually want to stop terror attacks by Muslims.

Speaking Monday at Saint Anselm College, Trump expanded his call for a temporary ban on Muslims to a ban on immigration from any region of the world with a history of terrorism against Americans. And tried to use this murderous rampage by a radicalized, homophobic, wife-beating, American-born Muslim as a campaign cudgel against Hillary Clinton.

“Clinton wants radical Islamic terrorists to pour into our country,’’ he charged. But that’s not all. As Trump told it, Clinton also wants to end the Second Amendment, take away Americans’ guns, and “then admit the very people who want to slaughter us.’’

“Let them come into the country, we don’t have guns, let them come in, let them have all the fun they want,’’ he said.

It’s hard to imagine a shabbier, less serious, more cynical response to a horrific event.

Trump didn’t stick around to take questions, but there defending him to a gaggle of reporters was former US senator Scott Brown, a Trump endorser and a participant in Trump’s conference calls for supporters and surrogates. I had a chance to ask Brown some of the questions I would have liked to pose to Trump. His answers were revealing.

How would imposing a ban on Muslims entering the US have kept Omar Mateen, who was born and resided in this country, from committing this horrible act? After ducking and dodging several times, Brown finally offered this: “Well, he [Trump] talked about the parents coming in here back years ago. Had we had a plan in place years ago. . . .’’

“Thirty years ago?’’ I asked. Mateen, after all, was 29 years old. His parents had immigrated to the US at some time prior to that.

“It doesn’t matter when,’’ Brown replied. Probably not, if a candidate merely wants to play on anti-Muslim sentiment. But if he is even pretending to be thinking seriously about how this rampage could have been prevented, it certainly does.

I noted that Trump’s speech lacked any mention of common-sense gun control, and that if Florida (or, for that matter, the US) had a law like Massachusetts does, local law enforcement could have investigated and interviewed Mateen, and would have had the discretion to deny him the license required to buy either of his weapons. (The assault rifle, almost certainly, would be banned here.)

“The fact that this guy was interviewed three times by the FBI and had the ability to go buy a firearm, obviously there needs to be some explanation there,’’ Brown replied.

Now, the FBI may well have missed something here. But here’s the crucial point: Despite the red flags that brought Mateen to the bureau’s attention, unless he was a felon or had a qualifying misdemeanor conviction or a restraining order against him, had been adjudicated mentally ill, or met one of a few other conditions, under federal law, the FBI could not have denied him the right to buy a firearm. What’s more, under current law, he could have a purchased a firearm even if he were (still) on one of the FBI’s terrorist watch lists.

So I asked Brown to explain how he thought Mateen’s bid to buy guns could have been thwarted.

“I don’t need to explain anything,’’ Brown replied. “The bottom line is, how did he get his hands on a weapon? . . . It’s common sense.’’

It should be common sense. But it won’t be, as long as the Republican Party is (1) in thrall to the National Rifle Association and (2) in charge of Congress.

Or if the GOP’s demagogic nominee-to-be gets away with using a murderous rampage to launch outrageous accusations, while diverting attention from the need for tougher gun laws.

Scot Lehigh can be reached at lehigh@globe.com. Follow him on Twitter @GlobeScotLehigh.