Authorities in the U.S. and Germany are scrambling to determine whether the shooting attack Wednesday that killed two U.S. airmen at the airport in Frankfurt was an act of terrorism.

The suspect is said to be a Muslim man with family in Kosovo who was born in Germany and was working at the airport at the time of the attack. He reportedly said “Allah Akbar” before opening fire on a bus outside the airport, a source told Fox News. The deadly attack also wounded two others before the man was taken into custody.

American officials in Washington told the New York Times that there was no immediate evidence tying the gunman to a terrorist organization. And German police added that they had no such evidence either, although they didn’t rule out the possibility of a link.

But a member of the U.S. House Homeland Security Committee, Rep. Patrick Meehan, said in Washington that it looked like a terrorist attack, though he noted that he still was being briefed on the details of the shooting.

A senior U.S. military official also told the Wall Street Journal that the suspect has “some kind of Islamic ties,” but was unsure how deep they were or if they were aligned with Al Qaeda or local terrorist groups in Kosovo.

“We don’t think they are particularly well-organized, but they are present,” the official told the Wall Street Journal.

The attack came as the bus sat outside Terminal 2 at the airport, according to Frankfurt police spokesman Manfred Fuellhardt. The bus driver and a passenger were killed, and one person suffered serious wounds and another light injuries, he said.

A source tells Fox News that the shooter yelled “Allah Akbar” when opening fire on the U.S. military personnel. He then dropped his gun at the scene, ran into the terminal and was subdued.

U.S. Air Force Europe spokeswoman Maj. Beverly Mock said all four victims were airmen.

They were all based at the Lakenheath military base in Britain.

A military official in Europe says the airmen were going to be deployed to either Iraq or Afghanistan.

President Obama said he was “saddened and outraged” by the shooting.

The president says the U.S. will spare no effort in finding out how the “outrageous” act took place and will ensure the perpetrators are brought to justice. He called it a tragedy.

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