A drone view shows people gathering to pay tribute to slain conservative commentator Charlie Kirk at the headquarters of Turning Point USA, ahead of a memorial service for him which is to be held on September 21,

U.S. President Donald Trump speaks as he arrives in Arizona to attend a memorial service for slain conservative commentator Charlie Kirk at State Farm Stadium, at Luke Air Force Base, Arizona, U.S., September 21,

Thousands of mourners, including President Donald Trump, attend the memorial service for conservative activist Charlie Kirk on Sunday.

Members of Congress are taking steps to tighten their own security as the killing of conservative activist Charlie Kirk has deeply shaken lawmakers who were already concerned for their safety

While speaking at Charlie Kirk's memorial, President Donald Trump said violence comes "largely from the left." Trump said Kirk talked to him about his previous death threats, but told Trump he "knew the risks" but would "never back down.

President Donald Trump is set to eulogize Charlie Kirk as a patriot and Christian martyr on Sunday as the political activist’s assassination continues to galvanize conservative support for the president.

Charlie Kirk's memorial draws tens of thousands to Arizona stadium as Trump and top officials deliver tributes. Follow Newsweek's live blog.