In many ways, the assassination attempt against Donald Trump at a Pennsylvania campaign stop was a perfect storm of failings coming together that allowed 20-year-old Michael Thomas Crooks to climb on top of a nearby building and take eight shots at the once and future president.
One attendee was killed, two others wounded and a bullet grazed Trump's ear before a Secret Service counter sniper opened fire on Crooks and killed him. That day jolted an already chaotic race for the White House and solidified Trump's iconic status in his party and beyond.
It also became a turning point for the agency tasked with protecting the president. As more details emerged about what went wrong, questions multiplied: What happened to the Secret Service's planning? Why was a rooftop with a clear line of sight to Trump left unguarded? What motivated the shooter?
Another incident in September where a gunman camped in the shrubbery outside one of Trump's golf courses before being spotted and shot at by a Secret Service agent also raised questions about the agency's performance.
A year after Butler, multiple investigations have detailed the breakdowns that day. Under a new leader hired by Trump, the agency has been pushing to address those problems but key questions remain.