Whether or not you had any responsibility in this really isn't that important here except perhaps as a learning experience. What you can focus on here is that what happened was truly upsetting and triggering for you, whatever the case. Talk to your therapist about the situation. It sounds like you really need to process the whole incident. Be gentle with yourself and honor your feelings about what happened. Try to put the placement of blame aside and focus on its effects and perhaps the causes. I'm sorry you went through such an upsetting incident. I'm sure it has left you quite shaken.