The Reddit user is RyanCox2021. He did write this as well, “If it makes it any more impressive, it was suit only without raising any suspicion didn’t wanna take anyones clothes because it would mess up my ‘experiment’ or whatever, and didn’t want any bodies being taken away in bodybags.”
‘There’s no witnesses if they’re all dead’.
In the post, he does say how he was able to do it suit only. Remember, at the start, they are all alive and he did not raise any suspicion. Also, sounds like he did it SA/SO.