KAISERSLAUTERN, Germany -- Two U.S. airmen testified at the trial of a man who allegedly shot them and killed two of their colleagues at Frankfurt Airport in March.

Staff Sgt. Kristoffer Schneider and Senior Airman Edgar Veguilla both suffered gunshot wounds when Arid Uka, 21, allegedly opened fire on a group of U.S. military personnel boarding a bus at the airport March 2, Stars and Stripes reported Tuesday.

Schneider, who has undergone a series of operations since the shooting, has to wear a helmet until surgeons replace the titanium plate in his skull to match the metal mesh and bolts holding the right side of his face together.

Giving evidence by videolink, he told the court Monday, "The right side of my skull is completely gone."

The airman was left mostly blind in his right eye and suffers from headaches, seizures, vertigo and a reduced sense of smell, the court heard.

In the fifth court date for Kosovan-Albanian Uka, Schneider testified that he heard the first shot as the men were loading their luggage onto the bus that was to take them to Ramstein Air Base en route to deployment in Afghanistan.

He said he heard the words "Allahu Akbar" [Arabic for "God is Great"] and saw a man shoot the driver in the head before turning the gun on the airmen.

Veguilla, who appeared in court, was shot him three times -- in the jaw, right elbow and back.

Uka has confessed to the shootings, in which Senior Airman Nicholas Alden, 25, and Airman First Class Zachary Cuddeback, 21, and the bus driver were killed and Schneider and Veguilla were wounded.

The airport post office worker was arrested as he was fleeing the scene and confessed to the killings during his first court appearance in August.

He said that he was influenced by jihadist propaganda on the internet and wanted to prevent American service members from going to Afghanistan, where he said he believed they would rape Muslim girls.

He also told the court that what he did was wrong.

The trial is scheduled to continue intermittently through January. The next trial date was scheduled for Dec. 5.