OREM, UT − Grief and anger flowed from the White House across the country as the assassination of conservative youth leader Charlie Kirk on a Utah college campus brought somber mourning and calls for revenge.

Kirk, 31, a close political ally of President Donald Trump, was killed by a single shot from a still-unknown gunman on Sept. 10 during an outdoor debate attended by 3,000 students at Utah Valley University.

Trump called Kirk “a martyr for truth and freedom,” and ordered flags flown at half-staff in his honor.

Kirk wasn't a Trump aide. He didn't have a college degree. But the conservative phenom built what he called "the largest pro-American student organization in the country," Turning Point USA, over the last decade, helping propel Trump to the White House.

More: She's a liberal. Charlie Kirk was her friend. After the shooting, she's honoring him.