Families of three slain U.S. service members and 13 others wounded in a mass shooting at Naval Air Station Pensacola in 2019 alleged Monday that the government of Saudi Arabia facilitated the attack, which U.S. authorities concluded was an act of international terrorism.

A 152-page complaint in federal court in Pensacola, Fla., makes new allegations that the shooter, Royal Saudi Air Force 2nd Lt. Ahmed Mohammed al-Shamrani, executed the attack with the support of “accomplices.” They included fellow Saudi air force trainees, whom he told of his plans at a dinner the night before and during a November visit to the 9/11 memorial in New York City to pay tribute to the hijackers, the plaintiffs alleged.

Shamrani, who was killed by responding sheriff’s deputies, worked with al-Qaeda in the Arabian Peninsula (AQAP) for five years to plan the Dec. 6, 2019, attack, U.S. authorities said in May after de-encrypting his phone.

The families also accused the Trump administration and the Saudi government of reneging on pledges of support for families.

“In the eyes of the American people, there is no greater betrayal than the realization that a purported ally is, in fact, an enemy, ” the lawsuit asserts. It seeks damages for an attack the families say was caused by Saudi Arabia and its willful or grossly negligent acts in sending a “Trojan Horse” terrorist operative into a U.S. program to train pilots flying warplanes that were part of U.S. arms sales worth billions of dollars.

“I think they knew he was out to destroy the American people and he was a terrorist. Innocent lives were lost. It should have never happened,” said Evelyn Brady, a 20-year Navy veteran whose son, Airman 1st Class Mohammed Haitham, 19, was killed while running unarmed toward the shooter with his hands up, pleading with him to stop.

“They were supposed to take care of the families. . . . They’ve done nothing,” Brady said in an interview with The Washington Post. Brady is represented with other plaintiffs by law firms led by Kreindler & Kreindler, which is also suing the kingdom on behalf of 9/11 victims and survivors.

A U.S.-based attorney for the Saudi government and a spokesman for the Saudi Embassy in Washington did not respond to a request for comment Monday.

The lawsuit comes as U.S.-Saudi relations have fallen to a new low since January, with the new Biden administration canceling arms sales, criticizing human rights abuses and the harassment of dissidents and pledging to “recalibrate” ties with the kingdom and its de facto ruler, Crown Prince Mohammed bin Salman.

The administration has said it will continue arms sales to the world’s biggest customer for U.S. weapons and signaled that it wants to continue a strong counterterrorism partnership. But it is also expected to make public as early as this week a long-sought U.S. intelligence report concluding that the crown prince ordered the 2018 killing of journalist Jamal Khashoggi, and to press Riyadh to end its war in Yemen and to moderate its own extremism.

A State Department spokesman said the agency declined to comment on pending litigation, but the Pensacola families’ allegations further complicate U.S.-Saudi ties. There are also pending federal lawsuits against the prince and other Saudis by Khashoggi’s fiancee and by a former top Saudi intelligence officer and close U.S. intelligence ally now living in Canada who claims he was also targeted for assassination.

Saudi Arabia has been frequently targeted by terrorist groups, including al-Qaeda, which carried out large-scale attacks beginning in 2003, and more recently by assailants sympathetic to the Islamic State group. Attacks have been directed at government facilities, Westerners stationed in the kingdom and members of Saudi Arabia’s Shiite minority, who are considered heretics by hard-line Sunni Muslims.

In January 2020, then-Attorney General William P. Barr announced that the 15-minute rampage at the Florida base was an act of terrorism, with the FBI concluding that Shamrani was motivated by “jihadist ideology.”

Barr and aides said that while it was initially reported that Shamrani arrived at the shooting site with others who filmed it, he in fact arrived alone and the investigation had not found evidence that anyone else acted with him.

Barr said 21 cadets from Saudi Arabia, including 12 from the Pensacola base, were unenrolled from their training and would be returning to the kingdom after U.S. officials said they found evidence that 17 Saudis had shared Islamist or anti-American material through social media. Fifteen — including some of those who had shared anti-American material — were found to have had contact with or to have possessed child pornography.

Barr said U.S. attorneys had reviewed each case and determined that such people would not normally be charged with federal crimes.

The families’ Pensacola lawsuit makes more-specific allegations. They claim that Saudi authorities knew of the radicalization of Shamrani — an al-Qaeda operative who made his first contact with AQAP by at least 2015 — and of anti-American and anti-Jewish statements he shared via Twitter.

Shamrani was nevertheless one of two out of hundreds of students in his Royal Saudi Air Force Academy class awarded a scholarship to enter a joint military training program in the United States, the suit asserts.

It also claims that the Saudi commanding officer on base and 11 other trainees it did not name knew that Shamrani purchased and stored a 9-millimeter handgun and ammunition on base in violation of U.S. and Saudi policy and that Saudi officials left the commanding officer’s post unfilled from September 2019 until after the shooting.

“None of the Royal Saudi Air Force trainees at the scene of the attack reported Al-Shamrani’s behavior nor did they try to stop the NAS Terrorist Attack. Because they supported it,” the suit asserts.

On Sept. 11, 2019, Shamrani posted a message on social media saying, “The countdown has begun,” and later that month sent a copy of his will to AQAP purporting to explain the coming attack, the suit alleges. That Thanksgiving weekend, the suit said, Shamrani and other trainees visited the memorial in New York City to those killed in the Sept. 11, 2001, terrorist attacks, in which 15 of 19 hijackers were Saudi nationals.

The suit alleges that during the visit, the trainees “discussed the plans for the NAS Pensacola Terrorist Attack.” It also asserts that on Dec. 5, the night before the attack, Shamrani hosted a dinner party for fellow trainees at which he screened videos of mass shootings and discussed his plans for the next day.

At least three trainees who attended the dinner called in sick the next morning, one of whom stood outside the building and recorded the shooting on his cellphone while two others watched from a nearby car, the suit claims.

That so many trainees were at least sympathetic to al-Qaeda and that several were “actually accomplices” demonstrates their belief that their extremist views “were in furtherance of [the kingdom’s] political and religious goals,” the suit claims.

Killed in the attack were Ensign Joshua Kaleb Watson, 23, of Enterprise, Ala., a recent Naval Academy graduate; Haitham, of St. Petersburg, Fla,; and Airman Apprentice Cameron Walters, 21, of Bryan County, Ga., days removed from boot camp and serving his first day on watch duty, whom Shamrani approached from behind and shot in the back of the head.

Four Navy service members, a Navy civil servant, seven sheriff’s deputies and a Defense Department police officer wounded in the attack also joined the suit. Two are partially disabled for life — Airman George Johnson, 26, and Jessica Pickett, 20. Johnson, a single parent who now must use a cane, was hit seven times, including with one bullet that was blocked by a metal “I love you” card from his mother in his wallet, the lawsuit said. Pickett, a Navy veteran and civilian employee, was struck nine times and has a metal rod in her left leg and a gap in her femur and requires a walker or wheelchair.

After expressing terrorist views for two years before being chosen for a coveted slot, training overseas to become a pilot, “an officer in their uniform murdered three Americans,” said Walters’s father, Shane Walters, 47, a former Navy F-18 Hornet mechanic and sales-team manager at Gulfstream Aerospace.

“Why? How did he get here? They had to have known. . . . It’s shameful,” Walters said in an interview with The Post.

Walters condemned the Trump administration, saying it failed to prioritize “dealing face-to-face” with the Saudis over the attacks. He also rebuked former president Donald Trump and the Saudi royal family for never personally speaking with the families of the killed or wounded U.S. service members.

The Trump administration was preoccupied with striking new arms and diplomatic deals and coddled Saudi Arabia “in a way no president ever has,” Walters said. “I don’t think my son’s murder, or Mo’s murder, or Joshua’s murder, was a top priority.”

The suit asserted that, adding “insult to injury,” Saudi Arabia has ignored or rebuked all attempts to discuss the families’ claims, as it purportedly promised to do in exchange for the United States allowing Saudi officers at Pensacola to immediately return home rather than face further investigation.

The suit cited Trump saying to reporters after a phone call with Saudi Arabia’s King Salman: “The king will be involved in taking care of the families and loved ones . . . likewise the crown prince. They are devastated by what took place in Pensacola. And I think they are going to help out the families very greatly.”

However, neither the U.S. government nor the kingdom of Saudi Arabia “contacted my family or talked to the other families,” Walters said. After the attacks, representatives of his son’s last private employer came to Walters’s home to give him two challenge coins from the vice president, Walters said, “one for me and one for my wife. They couldn’t do it themselves.”

Foreign governments and leaders are typically immune from civil suits in U.S. courts while in office. However, the lawsuit cited exceptions for terrorism and for victims of Saudi Arabia. It also cited a 1991 law called the Torture Victim Protection Act, which provides recourse in U.S. courts for violations of international law and for victims of “flagrant human rights violations,” including torture and summary execution abroad.

Kareem Fahim in Istanbul contributed to this report.

Correction: An earlier version of this report described Haitham as an airman apprentice. He was an airman first class.