I've read somewhere a person very close to him might actually be involved. Also the wife hired some ex feds to investigate in addition to the police. It indeed sounds like a scene from the action movie
I'd say that's very likely.
He probably talked about his wealth to the wrongs people and they've then set up the kidnapping to relieve him from his funds.
The fact that they still killed him after the ransom was supposedly paid is pretty terrible, but also somewhat logical actually.
If they had not killed him, investigators might have been able to find his kidnappers.
My condolences to his family, no-one deserves this.