He's basically making the claim that there will be violence if PA attempts to "cheat", and by cheat I mean count all of the ballots. It's a threat with plausible deniability.
has he done anything else the last 4 years?
Just more setting the stage to attempt to claim victory tomorrow night if things look favorable to him without all the mail-in ballots being counted.
CNN just had the Governor of Ohio and saying he had no idea what the fuck Trump was talking about.