Gee, what would be the first clue? Shouting “Allahu akbar!” while firing nine rounds into a group of American airmen on a bus? If that’s not good enough, ABC News reports that German intelligence had warnings of an al-Qaeda plot to “open fire in a public place.” Martha Raddatz reports at the very end that German security had been increased at airports based on this tip. Those dots get connected in Europe, where investigators are already treating the attack as an instance of Islamic terrorism, but the US is more reluctant to make the call:

Authorities in Europe are calling the shooting at a Frankfurt, Germany, airport that claimed the lives of two U.S. servicemen an act of Islamic terrorism, though U.S. investigators said it is too soon to tell.

The suspected gunman, 21-year-old Arid Uka, who was captured immediately after Wednesday’s shooting, admitted to the deadly attack and said he acted alone, German Interior Minister Boris Rhein said today, according to a report by The Associated Press. Uka, an ethnic Albanian from Kosovo who was described as a long-time resident of Germany, had been apparently radicalized over the last few weeks, Rhein said.

Uka allegedly shouted “Allahu Akbar” as he opened fire on a bus carrying U.S. airmen in Frankfurt, Germany, Wednesday, killing two and wounding two others before his gun jammed, officials said.

Uka also yelled “Jihad, jihad” when he was captured moments after the shooting in the airport terminal by an alert US airman and German police officer. But that’s still not quite enough for American officials to reach a conclusion:

The U.S. has launched an FBI-led investigation into the shooting and officials told ABC News it is too soon to determine whether the attack was an act of terror and if the suspect acted alone. However, a senior U.S. intelligence official told ABC News the attack was likely terror-related.

The reluctance to acknowledge this as an act of Islamist terrorism is truly puzzling. Doing so would not mean that the US had reached any conclusions about whether Uka acted alone or in a conspiracy. Clearly, whatever else motivated Uka, his view of Islam and its relation to the West appears to have been primarily in his mind; he wasn’t yelling “Taxes, taxes!” as he fired his guns, or “Yankee go home!” either. Denying the obvious doesn’t make for better investigations, but in this case it does make the US look weak and hesitant — certainly more so than the investigators in Europe, who don’t have a problem acknowledging reality.