IAMN[even_close_to_being]AL, but I think you're right about it being involuntary manslaughter. My very limited understanding is that when a drunk driver kills someone, it's involuntary manslaughter because they're undertaking a risky behavior with intent neither to kill nor cause bodily harm, but death occured as a result of that behavior anyway. I think it could only be voluntary manslaughter if the circumstances were wildly different, like if the man got swatted, had a heart attack or stroke or something life threatening after the police had left, and the perpetrators were the only ones watching the stream and decided, in the heat of the moment as they watched his death unfold, that they would let him die for some reason, like they were angry at him for having the audacity to keep streaming right after the swat... I dunno.
I believe it could only be murder if in the premeditated steps ("hey, let's swat this guy!"), the guys deliberately planned on using the swat to give this man a heart attack or serious bodily injury.
At least, that's my very limited understanding; I'm just some guy with a beard, I don't really know anything about anything.