Law enforcement officials have revealed that the gunman who attempted to assassinate Donald Trump used a drone to survey the rally site before the attack. This information was reported by various US media outlets.

The timeline of the drone surveillance conducted by Thomas Matthew Crooks, the 20-year-old shooter, remains uncertain. Investigators are working to determine whether the drone was flown hours or days prior to the July 13 rally in Pennsylvania, according to CBS, a partner of the BBC in the US.

Donald Trump, who is now the official Republican presidential nominee, has attributed his survival to “luck or God” after a bullet grazed his right ear during his campaign speech.

The attack led to the tragic death of a spectator and left two others seriously injured. Crooks was shot and killed by Secret Service agents at the scene. The actions of these agents and the overall security measures in place for the outdoor rally in Butler have since faced intense scrutiny.

Security Service Chief Kimberly Cheatle has been called to testify before a US House of Representatives committee on July 22 to address the incident.

Initially reported by the Wall Street Journal, investigators have informed CBS that they are still trying to pinpoint the exact timing of the drone flight. It is believed that Crooks flew the drone within days of the rally at the Butler Farm Show grounds. Other media outlets, citing security officials, suggest that the drone may have been flown on the day of the event.

The drone is thought to have been used by Crooks to identify the best vantage point for targeting the podium where Trump was speaking. Crooks fired multiple shots from the roof of a building approximately 130 meters (430 feet) from Trump.

In an interview with Fox News, set to be broadcast in full on Monday, Trump expressed his concerns about the incident. “How did somebody get on that roof? And why wasn’t he reported, because people saw he was on that roof,” Trump stated.

After the attack, the drone was discovered in the gunman’s vehicle and is now being examined by investigators. Additionally, two explosive devices, a tactical vest, and four magazines of ammunition matching those used in the attack were found in the vehicle