Several members of Congress vowed to question or investigate the United States Secret Service over the nearly successful assassination of former President Donald Trump.

Trump was fired upon at a rally in Butler County, Pennsylvania, but he turned his head at the last moment and the bullet meant for his skull instead nicked his ear. Secret Service admitted on Saturday that the shooter “fired multiple shots toward the stage from an elevated position outside of the rally venue,” raising questions as to why the position had not been secured.

House Homeland Security Committee Chairman Mark Green, a Republican from Tennessee, sent a letter to Homeland Security Secretary Alejandro Mayorkas emphasizing the “seriousness of this security failure,” noting that no assassination attempt has been so nearly successful since President Ronald Reagan was shot in 1981. Green said that there are “serious concerns regarding how a shooter was able to access a rooftop” within range of Trump.

The lawmaker requested documents detailing the security plan, communications about any potential increase of protective resources, and details about the rules of engagement used by Secret Service to “to assess and neutralize threats toward a protectee.”

House Oversight Committee Chairman James Comer, a Republican from Kentucky, likewise issued a statement saying he would call on Secret Service Director Kimberly Cheatle to appear for a hearing in the near future. Senate Homeland Security Committee Chairman Gary Peters, a Democrat from Michigan, will reportedly conduct an additional investigation.

Trump said in a statement on Sunday that “God alone” prevented the “unthinkable from happening” and mourned the death of Corey Comperatore, a firefighter from Sarver, Pennsylvania, who was struck by a bullet while protecting his family amid the chaos. Two other attendees, David Dutch of New Kensington, Pennsylvania, and James Copenhaver of Moon Township, Pennsylvania, were seriously injured but in stable condition as of Sunday.