WHCA dinner shooting live updates: Suspect planned to target as many people as possible: Sources

Handwritten notes found in the hotel room of the suspect in the White House Correspondents' Association dinner shooting Saturday appear to have been left with the intent that officials would find them, according to multiple law enforcement sources.

Sources tell ABC News that the suspect, Cole Allen, allegedly made brief statements to law enforcement officials after his arrest that he was focusing on Trump administration officials, and that he allegedly indicated that authorities would be able to find his thoughts in written form.

Sources say early evidence suggests that Allen's plans were to target as many people as possible in a mass shooting.

According to law enforcement sources, the alleged writings expressed a distaste for the Trump administration and also for Washington, D.C., elites.

Other similar writings were found in Allen's California home, sources told ABC News.

-ABC News' Jack Date, Pierre Thomas, Luke Barr, Aaron Katersky, Josh Margolin, and Katherine Faulders

President Ronald Reagan was shot outside the same Hilton Hotel of the White House correspondents' dinner in 1981.

In 1981, President Ronald Reagan was shot by John Hinckley Jr. outside the same Hilton hotel.

President Reagan was shot by John Hinckley Jr. on March 30, 1981.

The event prompted redesigning the property that increased security and added a special presidential suite near the entrance where chief executives could be taken.

Trump was dispatched there briefly after the incident Saturday night.

AP News contributed to this story.

Acting Attorney General Todd Blanche said Sunday that "the system worked" and kept President Donald Trump and other leaders safe from the shooting Saturday night at the White House Correspondents' Association Dinner that they were attending.

"The system worked; law enforcement and the Secret Service protected all of us. The man barely got past the perimeter. And so when you have a perimeter designed to keep people safe, like President Trump, and it works - that's something that should be applauded," Blanche told "This Week" anchor George Stephanopoulos.

Blanche said the suspect, whom law enforcement has identified as 31-year-old Cole Allen from Torrance, Calif., was likely acting alone, although investigations are ongoing.

"We believe that he traveled by train from Los Angeles to Chicago and then Chicago to Washington, D.C.," Blanche said.

Asked how the suspect may have gotten a firearm into the hotel, Blanche replied, "It's a good question. And listen, I'm not sure. It appears that he checked in on the 24th (of April) to the hotel, and we're still looking at video surveillance and footage of where he walked and how he got in and how those firearms got in, but at the end of the day, I expect we'll have a lot more about that in the coming days."

-ABC News' Oren Oppenheim

Cole Thomas Allen, the suspect in the White House Correspondents' Association dinner shooting, is being held the Washington, D.C., Metropolitan Police Department's Third District after being released form an area hospital overnight, according to law enforcement sources.

Allen is expected to appear in court on Monday.

A Secret Service Uniformed Division officer was also treated and released overnight from a different area hospital, according to sources.

-ABC News' Jack Date