After being in a high school for 3 years I decided to go back to school and get a degree in Mental Health Counseling. So many students were coming in to my office at that time with mental health issues that I felt that I needed more tools in my pocket.
Staying calm was number 1 giving students a five min break where they can sit, a five min walk, and five min of listening to music, reading or watching an appropriate video. This re sets your brain a bit at least enough to listen to perspective and move forward. Processing events can only happen when everyone is available so helping a student in the midst of a crisis to calm in the storm seems to work relatively well.
Keep calm and show support. Use open ended responses to engage the person in conversation which allows the individual to express themselves. Lastly, offer some community services to ensure the individual continues to get the help that they need.
Some interventions to apply during a mental health crisis include
Verbal de-escalation
Reality re-orientation
Offer change of environment/quiet time
Proper application of Crisis Prevention Institute (CPI) - Nonviolent Crisis intervention
Talk calmly and provide a quiet space for them to express themselves. Remove any sharp objects