Instant death may be useful if it’s like the Death Note, or else you’d also just get arrested.

At some point an investigator figures out that you're the only person that's connected to all the deaths, however remotely. As the years go by, you've done lunch together a few times and are on a first name basis. Their efforts are fruitless, and they can't prove anything. But now you have an FBI surveillance van permanently parked outside your home, and that investigator keeps coming around.