It may be scary, but it's probably worse for the person facing if.
  1. Stay close to the person
    some people prefer to be held however most people do not like physical contact. Remember to stay calm yourself and avoid adding to the uncertainty that they may be feeling.
  2. Speak to them reassuringly
    saying things like "you are okay" "keep breathing" and "it's okay to panic" have helped the most on the past
  3. Get them out of the chaos
    If they are triggered by something that just occurred, move them out of that setting. whether triggered or not, get the person to a quiet area.
  4. Get them water and tissues
    they are crying and they are dehydrated. I wouldn't say force it on them but coach them to drink it.
  5. Most importantly: let them talk to you after it all
    this is a very traumatic experience for them and it may be for you as well. Let them speak and vent. Keep everything as positive and remind them that everything is okay.