Our senior White House correspondent Kelly O'Donnell joins us with her latest reporting. We understand President Biden is on the move this evening.

It is unusual to see the president traveling very late at night, but these circumstances have warranted that, in his judgment, he will be leaving his Rehoboth beach, Delaware, residence and traveling back to the White House tonight. We expect that he will arrive here in Washington after midnight, returning to the White House sometime around 1230 in the morning. This is a change in his schedule. It is absolutely. As a result of the incident today, we heard from the president publicly in two forms already tonight, first a written statement, and then, as you were in the chair earlier, when he spoke to the small group of reporters with him in Delaware known as the traveling press pool, and he addressed the concerns about this incident and said that he was trying to reach former President Trump to speak to him directly and personally by phone. They had not done so at that point. He described how he has been briefed by the head of the secret service, secretary of homeland security, and also other officials, including his homeland security adviser within the White House, who would be steeped in the knowledge of any potential threats. The president saying that he, of course, wants everyone across the political spectrum throughout the country to stand against acts of political violence, saying, it cannot happen in America, should not happen in America.

So with that as the backdrop, the president will be traveling back here tonight. We don't have specifics about how his schedule might change further. He certainly had plenty of events coming up in the days ahead. So that will be kind of a piece by piece moment as they assess the status of the investigation. I expect the president would want to have additional briefings. And by coming back to Washington, he could speak directly with some of the officials who are based here separately. Ive been doing reporting that really began before this incident took place, about changes coming at the Secret Service because of the Trump candidacy, going from former former president who has a certain level of secret service detail, to the status of being the presumptive nominee, about to be formally the nominee of the republican party, and the fact that they had made plans to increase the size of his protective detail and the teams around him because of the change in campaign pace and because of the necessities of travel that certainly is borne out by these awful events today. In addition, three plane loads of chartered, on a chartered aircraft, three planes carrying secret Service personnel traveled yesterday from their various assignments to Milwaukee for the convention, where they were intended to be going, for a few purposes, of course, all the related security for the convention itself.

But also including the detail in waiting for the running mate selection, depending on the choice made by the former president about who he will run with on the ticket. And so preparing for that, for that person's immediate family to be by secret service, adding another protectee in the sphere of what the Secret Service does. So these are some of the moving parts that are happening. Big questions, of course, about how does the political calendar change because of that? What's happening with the investigative pieces, learning many more details about who has been harmed today, the innocent victims who have been caught up in this, as well as a real medical status on the former president, and any information that we can gain through our reporting with our law enforcement reporting colleagues about the suspected attempted assassin here, the gunman responsible, all of that unfolding on a Saturday night in a steamy Washington as we are trying to learn more details for the president to be back here. That, of course, gives him easy access to convene meetings with his officials and well stay on it as there are additional developments. Of course, the secret service provided some details that youve discussed at length tonight, having covered many Trump rallies when he was president and when he was a candidate in the last cycle.

These are such well attended events, huge crowds often, and covering events for the current president, President Biden, where he is out on the campaign trail. The security always includes a lot of screening. And that's why it was so notable that we were able to report that this gunman taken out and neutralized in the term of law enforcement by the Secret Service. Washington outside that perimeter, many questions still to be explored and investigation to be done. But President Biden will be returning here tonight, and we hope to have an update on whether he has reached the former president by phone. Lester.

All right, Kelly, thanks for watching. Stay updated about breaking news and top stories on the NBC News app or follow us on social media.