According to Regime Change, Trump was shaken by the assassination of Charlie Kirk.
He reportedly learned of the killing from his son Barron, who called in a panic and worried that Trump could be targeted again after surviving an assassination attempt in 2024.
Trump reportedly tried to reassure his son, telling him, “Calm down, honey, calm down,” but the authors write that he appeared unsettled by the news himself.
Source: NYT (reporting on Regime Change: Inside the Imperial Presidency of Donald Trump)