House Speaker Mike Johnson pledged Tuesday night that the House of Representatives would conduct an “immediate and thorough investigation” into security failures by the Secret Service prior to the assassination attempt Saturday evening on former President Donald Trump.

“We are united today as Americans in the wake of the assassination attempt on the life of Donald Trump,” Johnson said, speaking to the Republican National Convention. “Everyone, hear me clearly, and listen to me at home, and make no mistake. The House is conducting an immediate and thorough investigation of these tragic events.”

On Saturday, during a Trump campaign rally in Butler, Pennsylvania, a gunman open fire. A bullet grazed Trump’s ear. The shooter killed one of the attendees at the rally and injured two others.

The House Oversight and Accountability Committee, which oversees the U.S. Secret Service, has already announced it would investigate what mistakes the agency made in its efforts to secure the rally.

Secret Service Director Kimberly Cheatle has said she would not resign.

“That work [of the investigation] has already begun,” Johnson said. “The American people deserve to know the truth, and we will ensure accountability. I promise you that. This has always been an important principle to us. We in the Republican Party are the law and order team. We always have been, and we always will be advocates for the rule of law.” 

Toward the end of his remarks, Johnson added, “As President Trump raised his fist and gave a rallying cry on Saturday, now is our time to fight. And we will.”