I think Guiffre was killed by hacking into their vehicles to engineer a car accident. That's a thing now by the way, as incredible as it may seem that they would set up vehicles to be susceptible to being commandeered remotely.

60 minutes did a thing on it some years back. On a hacker they paid to take control of a new car they bought and were using in an empty parking lot where the hacker took control, of acceleration and braking and steering and the rest.