I mean the shooter was shot down so at least one of those shots had to be SS. But accounts on the scene said they heard a few quiet pops followed by louder ones from the counter sniper that was closer to them. Shouldn’t be hard to find a source if you look it up, I’m not able to at the moment.
This is the best I can find
So it could be that all 6 of the initial shots were from the shooter. I think its safe to say at least the first 4 were probably all him (and I do remember the number 4 from the accounts I heard), but the ones following are more ambiguous. Doesn’t look like they’ve released many specifics yet though.