The attack on a busload of U.S. Air Force troops at Frankfurt airport that killed two is being investigated as a possible act of Islamic terrorism, German federal prosecutors said Thursday.
Two airmen were also wounded late Wednesday when a man identified as a 21-year-old ethnic Albanian from Kosovo fired on the servicemen at close range.
"The suspect is accused of killing two U.S. military personnel and seriously injuring two others," federal prosecutors said in a statement.
"Given the circumstances, there is a suspicion that the act was motivated by Islamism."
Federal prosecutors said they had taken over the investigation of the Wednesday afternoon shooting, and are working on conjunction with Frankfurt and federal police, as well as American authorities.
The suspect was taken into custody immediately after the shooting and is to appear later Thursday in federal court.
Frankfurt police spokesman Juergen Linker told the DAPD news agency that one airman remained in critical condition after being shot in the head.
The other wounded airman was not in life-threatening condition, Linker said.
Both men were being treated at the Frankfurt University clinic. None of the victims have yet been identified.
The attacker's family in northern Kosovo identified him as Arid Uka, whose family has been living in Germany for 40 years.
His uncle, Rexhep Uka, said the young man worked at Frankfurt airport
and was a devout Muslim.
Police said the attacker had an altercation with U.S. military personnel in front of a bus outside the airport's Terminal 2.
They said the man started shooting, then boarded the bus briefly and was apprehended by police when he tried to escape.
The airmen were based in Britain, a U.S. Air Force spokesman for the Lakenheath airfield in eastern England said.
They were bound to Ramstein Air Base from where they were to have been deployed to support an overseas operation, the U.S. military said, without elaborating.
The U.S. has some 50,000 troops stationed in Germany. It operates several major facilities in the Frankfurt region, including the Ramstein Air Base, which is often used as a logistical hub for operations in Afghanistan and Iraq.
In Washington, President Barack Obama promised to "spare no effort" in investigating the slayings.
"I'm saddened and I'm outraged by this attack," he said.
Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.