This story was originally published by the WND News Center.

The United States Secret Service refused an offer to use drones from local law enforcement in Butler, Pennsylvania, at former President Donald Trump's campaign rally July 13, according to a whistleblower.

U.S. Sen. Josh Hawley, R-Mo., shared a letter to Homeland Security Secretary Alejandro Mayorkas with the allegation on Thursday.

He noted the FBI probe of the scene included evidence Trump's shooter, 20-year-old Thomas Crooks, used his own drone to survey the rally site just two hours before Trump took the stage.

"This raises the obvious question: why was the U.S. Secret Service (USSS) not using its own drones?" Hawley asked.

"According to one whistleblower, the night before the rally, U.S. Secret Service repeatedly denied offers from a local law enforcement partner to utilize drone technology to secure the rally," Hawley wrote.

"This means that the technology was both available to USSS and able to be deployed to secure the site. Secret Service said no. The whistleblower further alleges that after the shooting took place, USSS changed course and asked the local partner to deploy the drone technology to surveil the site in the aftermath of the attack.

"It is hard to understand why USSS would decline to use drones when they were offered, particularly given the fact the USSS permitted the shooter to overfly the rally area with his own drone mere hours before the event.