BUTLER, Pa. (AP) — Former President Donald Trump called for unity and resilience Sunday after an attempt on his life added fresh uncertainty to an already tumultuous presidential campaign and raised sharp questions about how a gunman was able to open fire from a rooftop near a Pennsylvania campaign rally. A full day after the shooting, the gunman’s motive was still a mystery, and investigators said they believe he acted alone before being fatally shot by Secret Service agents. President Joe Biden ordered an independent security review of the attack, which killed a bystander and critically wounded two others. The...