One of the officials confirmed the suspect is no longer in Syria.
“Army CID and Air Force OSI are conducting a joint investigation of the incident. A possible suspect, a US service member, has been identified,” the military said in a statement on Monday.
“At this point, these are just allegations, all suspects are presumed to be innocent until/unless convicted in a court of law. The investigation is ongoing, which may or may not, develop sufficient evidence to identify a perpetrator(s) and have enough evidence to ensure a conviction in a court of law. No further information will be released at this time,” the statement added.
Initially, US officials said they believed the April 7 attack was caused by indirect fire on the base in a similar manner to rocket and mortar attacks that have been carried out in the region by militia groups. However, a week later, a military statement said that after “further investigation” the attack was believed to a result of “deliberate placement of explosive charges by an unidentified individual(s) at an ammunition holding area and shower facility.”
The explosives used are described to CNN by two officials as “not insignificant” with more detonation power than a hand grenade. One official characterized the explosives as “military grade.”
The officials said the attack took place in the middle of the night and have uncovered security footage showing two instances of a figure moving quickly. It’s not clear if the two pieces of footage show the same person.
They are also looking into whether sentries were posted at either location. They say it’s not clear if the timing of the attack suggests the perpetrator was not trying to cause mass casualties or was looking to get away as quietly and quickly as possible.
None of the officials had any details about a possible motive for the attack.
The four injured service members were diagnosed and treated for traumatic brain injuries after the explosions but returned to duty later in April.
After the incident a “commander’s investigation” was initiated by the US Central Command, which oversees operations in Syria, but it was turned over to CID when it became clear the explosive pattern was not caused by incoming fire, officials say.
“The matter remains under investigation,” US Central Command said in a statement to CNN but offered no other details.
The Biden administration maintains around 900 troops in Syria, including special operations forces to advise and assist Syrian Democratic Forces.