I took a while to get involved in this because I have a similar case on the table, minus the airsoft guns.
What happened here is you got pissed on, without even the courtesy of having it called rain.
Your union rep will be able to help you. I'm glad you're onboard with this already.
As for legal advice, call up the Barreau de Montréal (http://www.barreaudemontreal.qc.ca/
). Ask for a referal for a lawyer that deals in "relations de travail" and that would be willing to work per commission. Usual rates from what I've gathered are 5% to 10%.
Before you sit down with a lawyer, put on paper any and all damages you have been dealt by this. Lost wages, medical costs and whatever. Also write down the timeline of all that happened. Note down every little detail, even those you might have omitted here.
The first consult with a lawyer on the island of Montreal is 30$ for 30 minutes. This is why you want to be organised. Ask about your options and make a plan.
Unless there is a specific reason to stay, I'd change jobs. One of the things you might be able to negociate in a severance package is a referal to another hospital. Set specific demands as far as wages, job type, hours are concerned.
Finally, take stock of what happened and remember to keep certain hobbies on the down low.