Thanks to congressional testimony on Wednesday from FBI Director Christopher Wray, more information has been revealed about the would-be assassin who attempted to kill former President Donald Trump at a campaign rally in Pennsylvania on July 13.

That includes the revelations that Thomas Crooks, 20, did online research about assassinations and conducted aerial surveillance of the rally site with a drone, that he had prepared some explosives that weren't used, and that he had access to multiple firearms owned by his father, according to the Daily Mail.

There remains plenty that is still unknown, however, such as what the shooter's motivation was, whether he had any assistance in his deadly actions, or how he was able to pull off the shooting from an elevated position despite the security measures of the U.S. Secret Service and local law enforcement.

Wray shared with Congress what the FBI has learned thus far

On Wednesday, FBI Director Wray testified for several hours before the House Judiciary Committee about a variety of topics, though most of the discussion was focused on the July 13 assassination attempt.

Among the biggest revelations were that Crooks appeared to decide on and begin planning the attack one week earlier on July 6, the day he registered to attend the Trump rally in Butler.

It was on that same day that the shooter conducted a Google search to learn some of the details of the assassination of President John F. Kennedy, including how far away suspected assassin Lee Harvey Oswald was from the presidential motorcade that he fired upon in Dallas, Texas.

Another big reveal was that Crooks had used a drone to surveil the rally site, and presumably his eventual rooftop perch, just two hours before former President Trump took the stage to begin speaking.

Firearms legally purchased by father

According to CBS News, Director Wray confirmed that eight spent shell casings were found along with a rifle and Crooks' lifeless body after the rally shooting occurred.

That rifle is believed to have been acquired by Crooks from his father last year, and was in addition to 14 other legally purchased firearms owned by the father that were found in a search of the family's home.

It is also believed that the shooter took that same rifle to a nearby gun range one day before the shooting.

The FBI director further testified that three "relatively crude" explosive devices were found -- two in Crooks' vehicle and another at the family home -- as well as an apparently unused detonator transmitter device on Crooks' body.

Motive remains unknown; shooter believed to have acted alone

As for what drove the shooter to want to kill former President Trump, Director Wray admitted, "We do not yet have a clear picture of his motive," as investigators have not yet found any revealing social media accounts, messages, or manifestos, though he added that agents were still looking and "digging in hard because this is one of the central questions for us."

Wray also seemed to confirm the reports that Crooks was a "loner" and acted without any assistance, as no evidence had been found that would indicate any accomplices or co-conspirators in the attack.