Trump Jr. says father is 'changed man'

Former President Donald Trump arrived in Milwaukee, Wisconsin on Sunday, one day before the Republican National Convention kicks off.

Trump's highly anticipated appearance at the RNC on Monday comes just two days after the assassination attempt of him at Saturday's campaign rally in Pennsylvania.

In a social media post Sunday, Trump indicated that he was going to delay his trip, but decided he wouldn't allow a "shooter" to change his scheduled plans to head to the RNC.

U.S. Secret Service and other officials said Sunday there are no plans to expand the security perimeter and that there are no known threats.

Canadian Prime Minister Justin Trudeau spoke with former President Trump on Sunday.

"The Prime Minister condemned yesterday's appalling assassination attempt and reiterated there's no place for political violence. The Prime Minister wished the former President well and offered condolences to the shooting victims and to the family of Corey Comperatore," Trudeau's office said in a statement.

Wisconsin Gov. Tony Evers is asking officials to revisit a prior decision that allows people to bring guns within blocks of the Republican National Convention in Milwaukee after an assassination attempt against former President Donald Trump, a person familiar with the matter told the Associated Press on Sunday.

Evers believes additional steps need to be taken to keep the convention's attendees, law enforcement and the local community safe, the person said. The person could not discuss details of the request publicly and spoke to the AP on condition of anonymity.

The request was made to the U.S. Secret Service, which would bring it to the Republican National Committee, the person said.

The Secret Service said at a news conference Sunday that they were confident in their existing security plan and hadn't made any changes following the shooting.

- Jesse Bedayn and Mike Balsamo

Authorities outside the security perimeter of Donald Trump's campaign event Saturday were alerted there was a man acting suspiciously before the shooting.

Local and state police, responsible for security outside that perimeter, began to search for a potential suspect, multiple sources briefed on the probe tell ABC News.

Within minutes, law enforcement spotted the suspected gunman on the roof, sources said.

It is unclear as of now, according to sources, whether this information was passed along to the U.S. Secret Service, which is responsible and focused on the security of the former president and the crowed inside the security zone.

A police officer saw the suspect on a rooftop and attempted to make it to the roof to engage the shooter, police sources said.

That officer was threatened when the gunman pointed his rifle at the cop, according to sources, who add that effort did not succeed as, moments later, shots rang out, targeting Trump.

-ABC News' Josh Margolin