One year ago in Butler, Pennsylvania, 20-year-old Thomas Matthew Crooks was able to get onto a nearby roof and take shots at Donald Trump. In the aftermath many wondered — who was this man who shot the presidential candidate, and how was he allowed to get so close to killing him?

Host Colby Itkowitz speaks with investigative reporter Carol Leonnig about the mystifying search for a motive and what she and others have concluded about what went wrong that day, one year later.

Today’s show was produced by Sabby Robinson. It was edited by Maggie Penman and mixed by Rennie Svirnovsky.

If you want to learn more about how the shooting in Butler changed Trump, our colleague Isaac Arnsdorf was on “Post Reports” on Friday to talk about that. His new book is “2024: How Trump Retook the White House and the Democrats Lost America.”

Subscribe to The Washington Post here.

If you can’t buy a graphics card…