First, ask your boss for your employer’s policies on handling these situations.
Second, ask your boss for de-escalation training. If you’ve already gone through this training, a refresher will still be good.
Third, you mentioned a union. Ask them for recommendations and resources.
Fourth, if your concerns feel unaddressed, contact whomever would be your HR department. Know that HR is not there to help or protect employees, but there to keep the organization from being sued.
Fifth, do right by yourself. You’re obligated to your own safety. Healthcare is an emotionally charged environment with clients who are almost never there for good reasons. These high level emotions will cause intense feelings and scenarios. People can react irrationally during such situations.
They aren’t a junior dev yet. They’re looking for a job as a junior dev and have been unsuccessful at finding a job as a junior dev.