President Joe Biden spoke directly to the nation Sunday, saying the political landscape cannot be a "killing field" after the assassination attempt against former President Donald Trump Saturday.

"Disagreement is inevitable in American democracy," Biden said, adding, "It’s part of human nature."

"But politics must never be a literal battlefield or God forbid, a killing field," Biden continued.

"I believe politics ought to be an arena for peaceful debate, to pursue justice, to make decisions guided by the Declaration of Independence and our constitution we stand for in America, not of extremism and fury, but of decency and grace," Biden added.

During his address, Biden said that he spoke on the phone with Trump following the attack and that he's "grateful" Trump was not seriously injured and doing well.

Biden ended his speech with a call for unity, saying, "Let's remember we are the United States of America."

"There is nothing, nothing, nothing beyond our capacity when we do it together," he added.

Former President Donald Trump was photographed as he disembarked from his plane that landed in Milwaukee, Wisconsin Sunday.

Trump can be seen in the photos with his fist raised on the plane's stairs.

The former president is in Milwaukee ahead of the 2024 Republican National Convention that is set to kick off Monday, just two days after an assassination attempt on Saturday.

During the attack at his campaign rally in Pennsylvania, Trump was wounded by a gunshot to the top of his right ear. He was treated at a local hospital after the attack.

Law enforcement sources tell ABC News that the FBI is currently in possession of three firearms from Saturday’s shooting and defense of the former president.

The firearms include one belonging to the shooter, one belonging to the Secret Service agent who shot and killed the shooter and the other belonging to a Butler County Sheriff’s Deputy who was involved in the shooting.

-ABC News' Luke Barr

The assassination attempt on former President Donald Trump "will likely be amplified in extremist messaging and heavily exploited by malicious actors," according to an NYPD intelligence product obtained by ABC News.

The misinformation surrounding the attack is "aimed at fomenting division," according to the Sunday bulletin.

"In the immediate hours after the shooting took place, multiple users on numerous online messaging platforms responded to the incident with support for the attack, overt calls for civil war, hostile rhetoric against FPOTUS Trump, threats against elected officials and generalized calls for retaliatory violence," according to the bulletin.

Sources have said there has been an uptick in threats to elected officials around the country as a result of the attack.

-ABC News' Luke Barr