He wast trying to use it as bait. It just happened that way. Bull will do that while reeling in smaller cutty's. Happened to a buddy last year. The bull didn't succeed but he tried.
Not tigers (brown X brook hybrid), rather a distinct subspecies Salmo marmoratus. Though it appears they can hybridize with browns (same ancestry). Largest one found was 24kg...they appear to live a life like a bull trout.