WASHINGTON (AP) — Charges against a man accused of shooting two National Guard members have been upgraded to first-degree murder following the death of one of the soldiers. The announcement by Jeanine Pirro, the U.S. attorney for the District of Columbia, came after Specialist Sarah Beckstrom, 20, died from injuries sustained in the attack.

Staff Sgt. Andrew Wolfe, 24, is still hospitalized in critical condition. The assailant, Rahmanullah Lakanwal, 29, now faces several charges including first-degree murder and possession of a firearm during a crime.

Pirro described the shooting as an “ambush-style” attack using a .357 Smith & Wesson revolver, adding that the motives behind the attack are still being investigated.

Lakanwal, who reportedly served in a CIA-supported Afghan Army unit before immigrating to the U.S., resided in Bellingham, Washington with his wife and five children. He entered the U.S. as part of the Operation Allies Welcome program, which aimed to evacuate Afghan allies after the U.S. withdrew from Afghanistan.

Many questions remain around the incident, including what drove Lakanwal to commit such an act. More details are expected to emerge as the case unfolds.