They're terrorists, because someone in authority thought so, and that's all it takes nowadays. No way will they be allowed in the U.S. except delivered in handcuffs to a long solitary confinement.
Did people actually brand them as terrorists? My knowledge of this story is an inital nytimes article when it happened and someone making a rather dramatic status about it on facebook. I am honestly baffled at how serious this seems to be for the police.