Trump shooter signed up online to attend rally a week before shooting: Source

An individual using the name of the 20-year-old Pennsylvania man who attempted to assassinate former President Donald Trump signed up online to attend the Butler, Pennsylvania, Trump rally on July 6, a week before the shooting, a source familiar with the matter tells ABC News.

The individual signed up using an encrypted email address and a cell phone number, the source said.

Three days after the Trump campaign publicly announced on July 3rd that the rally would take place on July 13, the individual using the email and cell phone signed up online, according to the source.

Federal authorities say Thomas Matthew Crooks shot Trump in the ear in an assassination attempt at the rally on Saturday. A rally attendee was also killed in the attack.

Ultimately, the building the suspect fired from was outside the security perimeter but was fewer than 400 feet from the podium where Trump was speaking, officials said.

ABC News previously reported that the suspect, Crooks, searched on his phone for images of President Joe Biden and former President Trump, and searched for the dates of Trump’s rally in Butler and the dates of the Democratic National Convention in Chicago, according to sources.

The phone search history revealed no indication of Crooks’ political views, and investigators were still trying to determine his motive.

The motive for the assassination attempt remains a mystery, according to the briefers, and they have not identified any ideological nexus to Trump and/or Biden.

The FBI told lawmakers they've conducted 200 interviews as part of the investigation, a source said.

An FBI spokesman did not respond to an email from ABC News seeking comment.