Seddique Mateen, the father of Pulse nightclub shooter Omar Mateen, was a longtime FBI informant, court documents show. (Alan Diaz/AP)

The father of the 29-year-old who killed 49 people at an Orlando nightclub in the summer of 2016 was an FBI informant who came under scrutiny himself after investigators found receipts for money transfers to Turkey and Afghanistan in the wake of the mass shooting, recently filed court documents show.

The revelation came in documents filed by attorneys for the shooter’s wife, Noor Salman, who is on trial in Orlando on allegations that she aided and abetted her husband’s attack and obstructed law enforcement’s investigation into it.

Prosecutors argue that Salman essentially admitted to the FBI that she knew what her husband was about to do. Defense attorneys argue that she was a victim of her husband’s abuse and infidelity and that false statements she made to the FBI came during a coercive interview.

The attack at the Pulse nightclub by her husband, Omar Mateen, is one of the deadliest mass shootings on U.S. soil. Mateen said before he was killed by police that it was done in the name of the Islamic State terrorist group.

Salman’s trial has been underway for weeks, but defense attorneys argued that they were not informed until Saturday of the father’s work for the FBI. That, they argued, is grounds to dismiss the charges against their client, or at least declare a mistrial.

“It is apparent from the Government’s belated disclosure that Ms. Salman has been defending a case without a complete set of facts and evidence that the Government was required to disclose,” defense attorneys wrote.

Late Monday afternoon, a judge denied their request.

Seddique Mateen — the father of Omar Mateen — was an FBI informant at various points between January 2005 and June 2016, court documents say.

Salman’s defense attorneys wrote that Seddique Mateen also had sent money to Turkey for a “substantial period and just one week before the attack,” and that in November 2012 an anonymous tip alleged that he was seeking to raise between $50,000 and $100,000 to help fund an attack against the government of Pakistan.

Prosecutors acknowledged the relationship between the FBI and Seddique Mateen in an email quoted in the defense attorneys’ filing. They also acknowledged that investigators searching Seddique Mateen’s home after the shooting found receipts for money transfers to Turkey and Afghanistan, which were dated between March 16, 2016, and June 5, 2016.

Based on those receipts, the FBI opened an investigation into Seddique Mateen, prosecutors wrote.

Efforts to reach Seddique Mateen were unsuccessful Monday. The FBI declined to comment.

After the massacre, Seddique Mateen had said in interviews, including with The Washington Post, that he saw his son the day before the incident and that nothing seemed amiss.

“He was well behaved. His appearance was perfect,” he said. “I didn’t see any sign of worrying or being upset or nervous.”

Salman’s attorneys argued in court filings that if they had known of Seddique Mateen’s work for the bureau, they might have explored a theory that Omar Mateen “conspired with his father, rather than Noor Salman, to commit the acts.”

Defense attorneys argued that they also might have explored whether the FBI’s interviews with Salman were an attempt at “evading the negligence they exercised with their own informant,” and whether their “unwavering focus on Noor Salman, rather than Seddique Mateen, could have been designed to find a culprit other than the father.”

The FBI has previously come under criticism for investigating Omar Mateen for 10 months starting in 2013 and ultimately concluding he was not a threat.

Defense attorneys frequently ask a judge to throw out a case before it goes to a jury, but such requests are seldom granted. Prosecutors’ failure to turn over relevant information, though, is considered a serious transgression, and attorneys for Salman argued that this was not the government’s first offense in the case.

Prosecutors, they said, also failed to initially notify them that forensic evidence contradicted Salman’s assertion that she had visited the nightclub before the shooting.

Closing arguments in Salman’s trial are expected this week.