The security guard wounded in a 2015 ISIS-inspired terrorist attack at the "Draw Muhammad" event in Garland, Texas, is suing the FBI, and argues the bureau is liable for his damages because an agent "solicited, encouraged, directed and aided members of ISIS in planning and carrying out the May 3 attack," according to court documents filed Monday.

If the plaintiff, Bruce Joiner, doesn't settle with the bureau, the case could shake loose hundreds of documents from both local and federal officials about what happened that day, and could answer the question of why an FBI agent was in a car directly behind the attackers and did nothing as the events unfolded.

In May of 2015, Elton Simpson and Nadir Soofi drove from their home in Phoenix to the Curtis Culwell center in Garland where the "Draw Muhammad" contest was being held, in a car loaded with three rifles, three handguns, and about 1,500 rounds of ammunition.

The two never made it inside, as guards, including Joiner, stopped them outside at a perimeter checkpoint, at which time Simpson and Soofi opened fire. Because the event was heavily guarded, the two were quickly shot and killed and barely made past the checkpoint where they opened fire.

Joiner was the only victim that day. He took a bullet to the left leg, and ISIS would later claim credit for orchestrating the attack, making it the first ISIS-backed terror event on U.S. soil.

Joiner's lawsuit is seeking just over $8 million in damages, and argues that the FBI essentially allowed the attack to happen.

"The FBI helped the terrorists obtain a weapon that was used in the attack by lifting a hold during a background check, incited the terrorist to attack the Garland event, and even sent an agent to accompany the terrorists as they carried out the attack," the court filing said.

The filing also alleged that former FBI Director Jim Comey lied in a "post-attack cover-up" about the bureau's knowledge of how the attack unfolded and what Comey and the bureau knew about what was likely to transpire.

"In the aftermath of the attack, former FBI Director James Comey lied to the American people by claiming that Simpson was a needle in a haystack' that was 'invisible to us,'" the filing alleged. "Even after it had come to light that an undercover FBI agent had been communicating extensively with the terrorists during the week prior to the event and had accompanied them as they carried out the attack, the FBI continued to assert that "[t]here was no advance knowledge of a plot to attack the cartoon drawing contest."

The FBI did not respond to a request for comment.

Since the attack, a separate court case and a "60 Minutes" report in March revealed that an undercover FBI agent was in the car directly behind Simpson and Soofi when they opened fire, and was even taking pictures of the car about 30 seconds before the first shots were fired. That case even revealed that the agent had texted Simpson just weeks before with the message, "Tear up Texas."

Shortly after the first shots were fired, the agent fled, and was briefly detained by Garland Police, as seen in a video still from WFAA TV in Dallas.

Because of a separate court case tangentially related to Simpson and Soofi, it's known that the FBI had been monitoring Simpson for years, and that the FBI agent was undercover in the Phoenix ISIS cell had direct contact with them routinely in the months leading up to the attack.

Joiner's attorney, Trenton Roberts told the Washington Examiner this year that he now believes the FBI might have been willing to let the attack unfold to even greater lengths.

"It seems like it had to have been one or the other," Roberts told the Washington Examiner in April. "Just a complete botched operation where they [the FBI] don't want the attack to actually take place, or, it's something where they need the attack to take place in order for this guy [the agent] to advance in the world of ISIS."

"And that's really what I think. I think that they thought, 'he's undercover and in order to advance, he needed to get pictures or video of this attack,' and then that would bolster his street cred within ISIS," Roberts said.

The events have even unnerved some congressional elected officials, as both Sen. Ron Johnson, Chairman of the Senate Homeland Security and Government Affairs Committee and Senator Chuck Grassley, Chair of the Senate Judiciary Committee, have both made inquiries to the FBI in an attempt to get to the bottom of the story.

Additional details of the court filing outline the facts that thus far loosely support a theory that the guns purchased by Simpson and Soofi may have been connected to the botched "Fast and Furious" operation by the Department of Justice, but the FBI and DOJ have been stubborn in their release of information that would clarify that issue.

The Washington Examiner has recently requested documents from the Garland Police Department. Many of those documents were not released, however, because the department claimed that the investigation into the event was ongoing, despite the fact that the "case status" indicator in the reports for both Simpson and Soofi are marked as "closed/cleared."

Open records advocates in Texas have called the use of the "pending" status to deny documents as a loophole that many police departments have used in the last twenty years after a minor change was made in the state's open record laws in the mid 1990's.