OK, I see that a legit source confirmed it.
There was an investigation about a kickback scheme that was going on at the hospital.
Which just happened to involve her doctor. I have to think the authorities would not have gone after Hillary's doctor without her OK.
An article by the Frederic paper said he was likely to be charged in the kickback scheme. That appears to be the motive.
It is also said that he left (suicide?) notes.