Trump Jr. says father is 'changed man'

New video licensed by ABC News shows police investigating near the building where the gunman was perched on the roof a full minute before shots rang out.

In one video, at approximately 6:10 p.m. and 26 seconds, police look onto the roof as a man in white shorts points toward the building.

The next clip begins just before 6:11 p.m. Bystanders are seen fleeing the area and the first gunshots are heard about 30 seconds into the video.

-ABC News' Victor Ordoñez and Christopher Looft

Security planners have reassessed and reexamined their plans for President Joe Biden's visit to Las Vegas this week in light of Saturday's shooting, a senior official briefed on the matter told ABC News.

Officials expect that there will be a heightened level of security and additional federal agents on site in Las Vegas, the official said.

Biden will be in Las Vegas from Monday to Wednesday for several events.

The House Oversight Committee will receive a briefing from the Secret Service on Tuesday, a source told ABC News.

Secret Service Director Kim Cheatle is then expected to appear for a public hearing in the House on July 22, the source added, citing conversations with the Secret Service. House Oversight Committee Chairman James Comer said on Fox News Monday morning that he's "100% confident" the hearing with Cheatle will happen.

The Secret Service will also brief GOP committee members later on Monday, a source familiar with House Committee on Homeland Security told ABC News.

First lady Jill Biden spoke with former first lady Melania Trump by phone on Sunday afternoon, a White House official told ABC News.

The White House did not share any further details about the call.