Sunday marks one year since the attempted assassination of Donald Trump in Pennsylvania

(NBC, KYMA/KECY) - Sunday marks one year since a gunman tried to assassinate then-presidential candidate Donald Trump at a campaign rally in Pennsylvania.

The president was grazed by a bullet during the rally in Butler as 20-year-old gunman Thomas Crooks fired eight shots.

One man, Corey Comperatore, was killed shielding his family and two other people, David Dutch and James Copenhaver, were shot.

A sniper subsequently killed the gunman, but the attack prompted questions about how Crooks was able to avoid detection by the country's top protective agency for nearly 45 minutes.

A new Senate report released Sunday morning says, "There was a disturbing pattern of communication failure" between federal, state, and local law enforcement agencies and "negligence that culminated in a preventable tragedy."

Additionally, the Secret Service denied or left unfulfilled multiple requests for additional staff, assets, and resources to protect President Trump

Two weeks after the shooting, Kimberly Cheatle, the director of the Secret Service, resigned.

This week, an official with the agency told NBC News the Secret Service suspended six people without pay for their actions.