Not that it's an excuse for what they did but why the hell would you suddenly spout "I am not a terrorist" when no-one has even implied as such. Yeah that's helpful to calming strangers in any situation, just suddenly say that without any reason.
Although, if you're trying to allay fears or play down your own 'threat', it probably helps to work your way up to terrorist through a series of denying smaller dangers instead of jumping straight to terrorist.