Trump rally shooter Thomas Matthew Crooks purchased 50 rounds of ammunition just hours before the incident, according to reports. 

Crooks, 20, bought the bullets from local gun shop Allegney Arms before opening fire at former President Trump in Butler, Pennsylvania, on Saturday evening, CNN reported.

FBI officials had not yet confirmed the report as of Tuesday morning, but noted that they've completed a vetting of Crooks' phone.

"The search of the subject’s residence and vehicle are complete. The FBI has conducted nearly 100 interviews of law enforcement personnel, event attendees, and other witnesses. That work continues," the FBI said in a statement.

TRUMP SHOOTER THOMAS MATTHEW CROOKS' PARENTS REGISTERED PENNSYLVANIA PROFESSIONAL COUNSELORS: RECORDS

Bruce Piendl, owner of Allegheny Arms, where Crooks bought ammunition before the attack, told Fox News Digital, "As a responsible member of our community, it is our prerogative to cooperate with law enforcement in every way. We are thankful that President Trump was not assassinated, and our hearts go out to all victims of this horrible incident."

"Out of respect for the ongoing investigation and that of those affected, we will not make any further statements," he added.

Crooks used his father's gun during the shooting, which injured Trump and two other men and left a rally attendee dead.

CNN reported that Crooks' parent owned roughly 20 registered firearms.

According to NBC, at least a dozen firearms were found in the Crooks' family home after a law enforcement sweep of the residence.

The FBI has also revealed that a search of Crooks' car turned up bomb-making materials that he drove to the site of the rally.

Investigators found that Crooks was in possession of a transmitter, but the purpose of the device was not clear.

The FBI has said he acted alone, but a motive for the shooting has not been specified as of Tuesday.

The 2022 high school graduate has been described as an insular loner who was subject to relentless bullying.

FBI HAS GAINED ACCESS TO THOMAS MATTHEW CROOKS' PHONE IN TRUMP ASSASSINATION ATTEMPT

While a registered Republican, Crooks donated to a progressive organization in 2021, further deepening the mystery around his motivations.

Crooks was shot dead by snipers after he opened fire at the rally at roughly 6 p.m. Saturday.

Trump was struck in the ear, while rally attendee Corey Comperatore, 50, was killed. Two others were hit and remain in stable condition.

Crooks' relatives have told various outlets that they remain mystified by the shooting, and haven't theorized about his motivations.

Fox News' Michael Ruiz contributed to this report.