the chief of the National Se-curity Guard (NSG), which fought the intruders, told me that he was certain there were six terrorists in-side. He said two terrorists hiding in the airmen’s billet,which was blown up, could have been caught alive had leitunent colonel Niranjan not died while handling the bodies of the four terrorists killed earlier.
In this sentence how the speaker using "have been caught alive had". can u express the meaning of sentence