This is the same thing as posting on a forum a question, then saying never mind I figured it out WITHOUT STATING THE ANSWER! When googling shit and coming across this back in the day I would get more mad at those than my issue.

“inject bystanders with empty syringes”

Injecting people with air can cause an embolism. The article may be wrong and this guy could’ve just been stabbing people with syringe however, if there was any kind of injection that was empty meaning air that can and will cause serious issues potentially death.