Looks like he shot the Buffalo 127 SCI with a New Zealander Scott Thomson & I would think at Mary River Game Park, by the Banteng & Deer he killed on the same trip ?

It would be a Bullock not a Bull, this is a Bull that is castrated at a young age (some times not so young) to grow bigger horns & body.

When I worked for the Buffalo abbattoirs, shooting Buff out on the plains, on my day off I shot a 120+DS Bullock that looked like it had its balls torn off, I would say by a Dingo, so could happen in the wild & I have seen 3 others over the years that I belive were Bullocks, all of them escaped or I didn't have a hunter with me .