FRANKFURT, Germany — A gunman opened fire on a bus at Frankfurt's airport on Wednesday, killing two U.S. airmen and wounding two others, German authorities said.
Police suspect a 21-year-old Kosovo-born man was behind the attack on a military bus that was taking the airmen to Ramstein Air Force Base, apparently after some kind of dispute.
It was not immediately clear if the gunman's motive was political. The assailant ran from the scene, but was overpowered and arrested by police in the nearby airport terminal.
Both German Chancellor Angela Merkel and U.S. President Barack Obama voiced shock.
The attacker shot three U.S. Air Force military policemen and the bus driver in the incident. About 12 military police who had just arrived on a commercial flight from London were on the bus.
U.S. European Command in Stuttgart confirmed the deaths but did not release the names of the victims, pending family notification.
Boris Rhein, interior minister of Hesse state, where the attack occurred, said the suspect first spoke to an airman standing outside the bus before shooting. He then shot the bus driver, Rhein told Germany's Hessischer Rundfunk television.
There was no indication why the assailant was carrying a pistol. German gun laws license very few people to walk around armed.
But a German news website, Spiegel Online, said investigators presumed the gunman was deliberately seeking members of the U.S. armed forces as victims. It added that he had been carrying extra ammunition. The Frankfurt police would not confirm the report.
Over recent years, German police had foiled every one of several Islamist plots aimed against U.S. servicemen on German soil.
Rhein said the suspect had roots in Kosovo and lived in the Frankfurt area. He was interrogated for hours by police.
The bus passengers were on their way to deployments in Iraq and Afghanistan, with orders to fly from nearby Ramstein Air Force Base, the biggest U.S. military airfield in Europe, Air Force spokesman Wolfgang Hofmann said.
All were members of the Security Forces, the military police section of the Air Force, and had been based at Lakenheath, England.
At the scene, Rhein stressed that he was not using any words to suggest it was a terrorist attack and was calling the incident a homicide only, but added, "At the moment, I don't rule anything out."
Police spokesmen said one victim was found dead on the road in front of the bus. The wounded men were shot in the head and in the chest respectively. One was in critical condition.
Nine shots were fired and the suspect still had the pistol used in the attack with him when he was arrested.
The incident occurred in a bus lane in a publicly accessible part of the airport, outside Frankfurt Terminal 2. There were 10 to 15 occupants in the bus.
Merkel said: "Today there was an incident in which two American soldiers were killed at Frankfurt Airport.
"I want to express my shock and say that we will do all we can to investigate what happened. It is a dreadful incident and Germany will do all it can to bring clarity to this matter."
Obama told reporters in Washington he was "outraged" over the slayings and vowed to cooperate with the German government to investigate the case. "I am saddened and I am outraged," Obama said at the White House.
"We will spare no effort in learning how this outrageous act took place and in working with German authorities to ensure that all of the perpetrators are brought to justice," he said.
Kurt Beck, premier of Rhineland Palatinate where the base is located, said, "We will be doing all in our power to protect U.S. citizens in our state."
U.S. military buses regularly shuttle to the airport from U.S. bases, picking up personnel coming in on commercial flights and dropping off servicemen and servicewomen heading home to the United States.
Operations at the huge airport continued uninterrupted after the incident. The airport is Germany's biggest, serving 119 airlines and processing 150,000 passengers every day. The crime scene was cordoned off as police gathered evidence.
Kosovo also condemned the killings. "The government of Kosovo is deeply touched and condemns the murder ... and the wounding of two others by a Kosovo citizen," it said in a statement, calling the attack "a ghoulish individual act."