Tail rotor strike on the compound wall as he overcooked it on the way in.
Some of you may recall the two tailwheel holes in the wriggly tin wall at Dungannon. OC 72 and STANO. Libellous in this day and age, but I was FLANG (Flight Lieutenants Against Non-Graduates) as opposed to FOLA, a bunch of virgins who couldn't read or write. Or fly very well come to think of it. Hat on.
Looks to me like he left the tail rotor on the outside of the compound while he (or she, obviously) enjoyed a relatively short and low speed crash to where the fun was. Epic entrance.
I've never heard a super stealthy helicopter, especially when there's four of you and two of you are Chinooks and it's in the wee small hours.