They shoot at him because they're worried that Cyclonus would kill them if he had a chance to attack. BUT... they only shot at him in the first place because he tried to Megatron. Triggerhappy or not, that should be something even they can overlook, right? The security team must be part of those who fear Cyclonus as said earlier in the issue rather than being his friend. Just because Cyclonus looks dead doesn't mean he is actually dead. James Roberts is the master of fake-outs.