Yes, that character hung around the whole fight in a Rifter, just to whore on the kill at the end.
No, you can attack a vulnerable structure in highsec without a wardec and apply damage. You just have to deal with the consequences of CONCORD as usual.
A word of caution though: if you do want to do this, make sure to wait until the end. There is a 15 minute window or so on applying damage to get on the killmail. You will notice that most of the fleet did not make it on the kill mail despite apply significant damage as due to a third-party arriving, there was a break in the shooting as the fleet had to dock up and a few characters had to switch corps. If you CONCORD yourself too early, you won’t be on the killmail either.