Trump shooting live updates: Two still in critical condition; campaigns on high alert

This is CNBC's live blog tracking developments after an assassination attempt against former President Donald Trump. See below for updates.

The attempted assassination of former President Donald Trump at a rally in Pennsylvania on Saturday left one attendee and the gunman dead, and two more attendees still in critical condition 12 hours later.

Trump was grazed by a bullet and treated at a local hospital, but released late Saturday night.

The nation is shaken and elected officials and law enforcement are on high alert from Washington to California for any additional threats.

The FBI has identified the shooter, now deceased, as 20-year-old Thomas Matthew Crooks of Bethel Park, Pa., a registered Republican. He used a semi-automatic weapon, NBC News reports.

"We're all Americans, and we have to treat one another with dignity and respect," House Speaker Mike Johnson (R-La.) said in an interview Sunday on NBC News' "Weekend Today."

Just a day before the Republican National Convention begins in Milwaukee, several Republicans and Trump allies blamed Democratic rhetoric that they said demonized Trump, for inciting the violence.

CNBC's politics reporters and breaking news teams are covering the day's developments from Washington, D.C. and New York City.

Former Vice President Mike Pence said he and his wife "thank God" for Donald Trump's safety and sent their condolences and support to the victims and their families.

He added a note of gratitude for the Secret Service's "swift response," which he added, "undoubtedly saved lives."

"There is no place in America for political violence and it must be universally condemned," he added.

Pence was one of several government officials targeted by armed rioters during the deadly Jan. 6