A number of these are threatening comments made against the President of the United States.
As such the US Secret Service is obligated to investigate. And unless whoever is posting them is very knowlegable about maintaining Internet anonymity in the face of the resources the USSS can bring to bear in tracking them down, they’ll have left a nice set of ip breadcrumbs back to themselves.
We’ll see what comes of that ...
Check Hillary’s server. I’m sure she has several Twitter aliases.