Biden orders independent review of attempted Trump assassination

• Biden said he has also ordered the Secret Service to analyze security measures at the convention, scheduled to kick off Monday in Milwaukee.

What they're saying: "An assassination attempt is contrary to everything we stand for as a nation," Biden said Sunday, flanked by Vice President Kamala Harris and Attorney General Merrick Garland after receiving an updated briefing on the Pennsylvania attack.

• "We cannot allow this to happen," he continued. "Unity is the most elusive goal of all."
• The president did not take questions but said he would speak "at greater length" Sunday night about the need for Americans to come together in an address from the Oval Office.

Biden also offered his condolences to the family of Corey Comperatore, the man who died after diving on his wife and daughter to protect them from gunfire at the rally.

• "He was a father; he was protecting his family from the bullets that were being fired, and he lost his life," he said. "God love him."

Catch up quick: Biden said he spoke with Trump Saturday night, hours after the former president left the scene, his ear and face bloodied.

• Biden characterized their discussion as a "short but good conversation."
• During brief remarks Saturday, Biden condemned the violence, saying, "It's sick. It's one of the reasons why we have to unite this country."

The bottom line: Saturday's attack left the president's campaign entangled in a fragile political and ethical web.

• A campaign official said the Biden-Harris campaign is pausing television advertising and all outbound communications in the wake of the attempted assassination.
• Biden's response to the attack could soothe concerns about his age and mental acuity — but he also must consider the timing of his return to the campaign trail, where he has slammed the former president as morally unfit for the job.

Go deeper: What to know about Secret Service Director Kimberly Cheatle