It's impossible to specify multiple signals when using kill.
There's a bit of a problem with using the word simultaneously
here. In short: there's no such thing, even if kill allowed specifying different signals for different processes, it would still send one of those signals before the other. So using...
kill -9 8888; kill -2 5555 // always executes both
kill -9 8888 && kill -2 5555 // executes the next command only if the previous one succeeded
... would give you preeeeeetty much the same result as something like this:
kill -9 8888 -2 5555 // not possible anyway