You don't need anything more than hearsay to arrest and charge someone with a crime.
In fact criminal complaints are by their very definition hearsay.
Judges set bail, people sit in jail and plead guilty to crimes based on nothing more than hearsay.
At arraignment, judges decide whether to set bail on the basis of these allegations. If they do, and you can't make bail, you are held in jail.
If you are charged with a misdemeanor, you might be able to get out of jail at arraignments so you could "choose" to plead guilty even if you are innocent so you don't have to stay in jail.
It is beyond easy for the prosecutor to secure an indictment against you, unless you are a police officer.
Impeachment? I guess it is some small reckoning for a person who is guilty of crimes beyond anything I can begin to fathom.
That's also a massive abuse of power and it's just as urgent and compelling that we do something to fix it.