During a mass shooting or other large scale casualty event, witnesses can become more than innocent bystanders.
"The people who are going to be able to render aid are the ones that are there," says Jennifer Turner, Trauma Program Manager at Medical City Lewisville.
She teaches one of several first aid classes available for free to the public.
They teach "Stop the Bleed" techniques and hands-only CPR.
The “Stop the Bleed” campaign was launched during an event at the White House, to provide bystanders of emergency situations with the tools and knowledge to stop life threatening bleeding.
"Tourniquets can only be applied to hands and legs. They will stop the bleeding," says Turner, who demonstrates the techniques for us.
"It's going to apply a lot of pressure around that leg and it will make the veins stop bleeding"
Another technique they teach is correctly packing a wound. "Identify where the wound is, then take your clothing or gauze and start packing it inside the wound," says Turner, who also teaches use of a defibrillator and hand-only CPR.
"Studies have shown that compressions alone can help save that life, so we teach you the right way on how to do chest compressions."
According to the Department of Homeland Security, if you would like to take a course to prepare yourself to assist injured people following a traumatic event, contact your local public health department, hospitals and clinics, emergency medical services, or fire and police departments to see if they offer any training.
You can also check here for a class near you.