Donald Trump really unloaded on the media yesterday, and there was, in my view, one overriding reason.

He was really ticked off.

We can talk about how the fourth estate makes a juicy target for the billionaire, how his base loves the attacks on journalists, and how important it was for him to put the controversy over his donations to veterans behind him.

But I’ve seen Trump rip the press many times, including in interviews with me, and there is no doubt in my mind he was angry.

“The press should be ashamed of themselves,” he declared at Trump Tower. 

"Instead of being, like, 'Thank you very much, Mr. Trump,' or 'Trump did a good job,' You say, 'Well, who got it? Who got it?'. ... And it makes me look very bad. I have never received such bad publicity for doing such a good job."

It is, of course, the job of journalists to ask tough questions of presidential candidates. But in the way that Trump views the world, he tried to do something honorable—raise money for vets—and was unfairly rewarded with negative headlines.

Thus, he went off on the “dishonest” press and called ABC correspondent Tom Llamas a “sleazy guy,” saying: “"You're a sleaze because you know the facts, and you know the facts well.”

Even as president, Trump said, “I’m going to continue to attack the press.”

The takeaway is that Trump had raised $5.6 million for veterans’ groups, and obviously enjoyed reading off the names of the organizations and who had gotten the checks. He said it had taken time to screen some of the groups.

Trump made his own million-dollar donation on May 23, after the Washington Post had raised questions about the process on Twitter—and in a news story the next day.

At the presser, Trump repeatedly said he wanted this to be a low-key effort and wasn’t looking to grab credit. But the effort grew out of an earlier skirmish with the media, namely Fox News.

It was on Jan. 28 in Des Moines, when Trump was complaining about Megyn Kelly and Fox’s fairness, that he skipped the Iowa debate and instead put together the vets’ 

fundraiser, which became a competing televised spectacle. It was there that he announced $6 million had been raised, so this wasn’t exactly under the radar.

There was, naturally, pushback from the press. Washington Post columnist Chris Cillizza wrote that “if he said he raised/donated $6 million to charity for veterans group — the support of which he has put at the center of his campaign — then the media's job, LITERALLY OUR JOB, is to find out who he gave to and how much.  Simply taking Trump at his word — ‘I'm accountable,’ he insisted Monday — isn't good enough.” 

Hillary Clinton, phoning in to CNN’s Jake Tapper, complained about “the difference between what Donald Trump says and what Donald Trump does.” She said he’s “bragged for months” about raising the money and making his own donation, “but it took a reporter to shame him into actually making his contribution and getting the money to veterans.”

The important thing here is that Trump did right by the vets, one of his core constituencies. It could be argued that he stepped on that message, in part, by relentlessly slamming the journalists. But such an approach has always worked for him.

What happened on Fifth Avenue may signal a new phase in Trump’s relationship with the press. Once he clinched the nomination, there were no more disputes about biased polls and crowd estimates. Trump eased up on the criticism, made peace with Megyn Kelly and said the media were treating him relatively fairly.

But he pushed back hard against the New York Times after its story on his treatment of women, especially when the ex-girlfriend cited at the top of the story said her interview had been misrepresented. He also called Bill Kristol a “loser”—and bashed him again yesterday—as the Weekly Standard editor has openly tried to recruit a third-party conservative challenger (and now appears to be touting National Review writer and Iraq war veteran David French, not exactly a political heavyweight).

Perhaps Trump thinks the press is ratcheting up against him now that he’s the de facto nominee and he needs a strong defense. Perhaps, with no remaining Republican rivals, he believes he needs to fire up his supporters by denouncing media dishonesty. 

Or maybe he’s just mad as hell.

Howard Kurtz is a Fox News analyst and the host of "MediaBuzz" (Sundays 11 a.m. and 5 p.m. ET). He is the author of five books and is based in Washington. Follow him at @HowardKurtz. Click here for more information on Howard Kurtz.