You can see it in Hillary's tweet. I think she had him taken out and then put out this tweet that pretends to be consoling, but is really a warning to anyone who is thinking of betraying the Clintons. "What a loss" is talking about his usefulness as an asset. Like a cheap hollywood gangster movie: "So sad that Joey had an unfortunate accident"

My question would be "what did he find out that would have dramatically shifted his allegiance away from Hillary?".