In a tragic incident on Saturday near the ancient city of Palmyra in the Syrian desert, two U.S. military personnel and one American civilian lost their lives, while three others sustained injuries. The confrontation, which also left three Syrian security officers wounded, unfolded during a clash with the assailant, according to Nour al-Din al-Baba, spokesperson for the interior ministry.

Al-Baba highlighted the challenges faced by Syria’s newly established authorities, who have been grappling with a shortage of security personnel. This situation arose after a surprising turn of events last year when a rebel offensive, initially aimed at seizing the northern city of Aleppo, unexpectedly led to the overthrow of former President Bashar Assad’s government.

“We were taken aback when we managed to seize control of the entire country in just 11 days, burdening us with significant responsibilities in terms of security and administration,” he remarked.

The assailant was one of 5,000 recent recruits to a newly formed division within the internal security forces stationed in the Badiya, a desert region where remnants of the Islamic State group continue to operate.

Attacker had raised suspicions

Al-Baba noted that suspicions of an infiltrator leaking information to IS had surfaced within the leadership of the internal security forces, prompting a comprehensive evaluation of all members serving in the Badiya area.

The probe raised suspicions last week about the man who later carried out the attack, but officials decided to continue monitoring him for a few days to try to determine if he was an active member of IS and to identify the network he was communicating with if so, al-Baba said. He did not name the attacker.

At the same time, as a “precautionary measure,” he said, the man was reassigned to guard equipment at the base at a location where he would be farther from the leadership and from any patrols by U.S.-led coalition forces.

On Saturday, the man stormed a meeting between U.S. and Syrian security officials who were having lunch together and opened fire after clashing with Syrian guards, al-Baba said. The attacker was shot and killed at the scene.

Al-Baba acknowledged that the incident was “a major security breach” but said that in the year since Assad’s fall “there have been many more successes than failures” by security forces.

In the wake of the shooting, he said, the Syrian army and internal security forces “launched wide-ranging sweeps of the Badiya region” and broke up a number of alleged IS cells.

A delicate partnership

The incident comes at a delicate time as the U.S. military is expanding its cooperation with Syrian security forces.

The U.S. has had forces on the ground in Syria for over a decade, with a stated mission of fighting IS, with about 900 troops present there today.

Before Assad’s ouster, Washington had no diplomatic relations with Damascus and the U.S. military did not work directly with the Syrian army. Its main partner at the time was the Kurdish-led Syrian Democratic Forces in the country’s northeast.

That has changed over the past year. Ties have warmed between the administrations of U.S. President Donald Trump and Syrian interim President Ahmad al-Sharaa, the former leader of an Islamist insurgent group Hayat Tahrir al-Sham that used to be listed by Washington as a terrorist organization.

In November, al-Sharaa became the first Syrian president to visit Washington since the country’s independence in 1946. During his visit, Syria announced its entry into the global coalition against the Islamic State, joining 89 other countries that have committed to combating the group.

U.S. officials have vowed retaliation against IS for the attack but have not publicly commented on the fact that the shooter was a member of the Syrian security forces.

Critics of the new Syrian authorities have pointed to Saturday’s attack as evidence that the security forces are deeply infiltrated by IS and are an unreliable partner.

Mouaz Moustafa, executive director of the Syrian Emergency Task Force, an advocacy group that seeks to build closer relations between Washington and Damascus, said that is unfair.

Despite both having Islamist roots, HTS and IS were enemies and often clashed over the past decade.

Among former members of HTS and allied groups, Moustafa, said, “It’s a fact that even those who carry the most fundamentalist of beliefs, the most conservative within the fighters, have a vehement hatred of ISIS.”

“The coalition between the United States and Syria is the most important partnership in the global fight against ISIS because only Syria has the expertise and experience to deal with this,” he said.