President Joe Biden said he had a "short but good conversation" with former President Donald Trump on Saturday night in the wake of the shooting.

"I am sincerely grateful that he's doing well and recovering," Biden said in an address to the nation on Sunday.

President Joe Biden said he had a "short but good conversation" with former President Donald Trump on Saturday night in the wake of the shooting.

No motive is known, Biden said, and he urged the public to not make assumptions.

Biden said he's directed the head of the Secret Service to review all security measures for the Republican National Convention, which begins on Monday in Milwaukee.

"We'll share the results of that independent review with the American people," Biden said.

He added, "I've been consistent in my direction of the Secret Service to provide [Trump] with every resource, capability and protective measure necessary to ensure his continued safety."

Biden said he will speak from the Oval Office at 8 p.m. ET on Sunday.

President Joe Biden is rescheduling his Monday trip to Austin, Texas, where he was scheduled to deliver the keynote address at a commemoration for the 60th anniversary of the Civil Rights Act, according to the White House.

This is Biden's first rescheduled event in the wake of the assassination attempt on former President Donald Trump. It also follows Vice President Kamala Harris postponing her Tuesday campaign stop in Florida.

Biden is expected to deliver remarks to the nation at 1:30 p.m. ET Sunday.

Former classmates of the suspected shooter, 20-year-old Thomas Matthew Crooks, of Bethel Park, Pennsylvania, described him to ABC News as a student who was "quiet" and did not have many friends.

"He was somebody who came across as lonely a lot," said Jameson Myers, who said he attended both elementary and high school with Crooks.

Myers described him as "more socially reserved" and someone who "didn't have a ton of friends."

MORE | What we know about the Trump rally shooting suspect

But he said he never heard Crooks discuss politics or, specifically, Donald Trump.

"I was friends with him. He never acted, like, by any means, a political revolutionary," Myers said. "Was a very nice, even sweet guy, from what I knew."

Another classmate, Zoe Materkowski, said he was "just a quiet kid."

Added Jason Kohler, a classmate: "He was a loner. He would sit alone at lunch."

Classmate Robert Abraham described him as "smart" and "kind."

Pennsylvania Gov. Josh Shapiro has identified the man killed yesterday in the shooting at the Trump rally as Corey Comperatore and said he had just spoken with Comperatore's wife and two daughters.

"Corey was a girl dad, Corey was a firefighter, Corey went to church every Sunday," Gov Shapiro said. "Most especially Corey loved his family."

Shapiro said Comperatore died a hero.

"Corey dove on his family to protect them last night at this rally. Corey was the very best of us."

MORE | Governor says man killed at Trump rally was former fire chief who 'died a hero'

Pennsylvania Gov. Josh Shapiro says the man who was killed at a rally for former President Donald Trump "died a hero" and that Corey Comperatore dove onto his family to protect them.