In 2010 I was attending an instructor's conference when there was that time where people went around the room and introduced themselves. We were supposed to say who we were, what our shooting backgrounds were, if we were with any departments/organizations, what we were looking to get out of the course and what we were working on/what skills or certifications we were pursuing back home. Everyone in the class addressed very specific firearm skills, and finally one guy broke from the groupthink and stated that he was working on becoming an EMT. The course instructor kind of said, "Ok, moving on..." and little more was mentioned. On day 4 or 5, I was speaking with the instructor who said he was working on becoming an EMT and I sort of said, "Oh, what made you want to become an EMT?" His explanation puzzled me.
He explained that things can and do go wrong at ranges and that if you were going to spend most of your time on a firing range, you would be wise to mitigate the possibility of complications (or even death) from a wait in medical response time.
My response was something to the effect of, "Err, ok."
Several weeks later, his words finally sunk in. I spent a TON of time shooting. Getting a small amount of medical training (preparing) for an event that may never happen was the exact same logic I had used every day when I strapped on a firearm. I had prepared myself to carry every day, I owned a fire extinguisher and regularly changed the batteries in my smoke alarms...how was this any different?
I eventually signed up for an EMT course that was a few nights a week for a few months. Not only was I well prepared in terms of understanding a full overview of what is happening to the body when someone has been shot, I understood various ways to treat it and then how to interact with other rescuers, all the way from police and EMS responding, all the way into the hospital and then interacting with hospital personnel. In addition to attaining my main goals of being able to respond to a catastrophic accident at a range, I suddenly realized that I knew a lot of medical things that had unintentionally enriched my life.
Later, for the sheer enjoyment of enriching my life with more medical knowledge, I finished paramedic school, which is after EMT school or Advanced EMT school and is like EMT school on steroids, with less sleep for a much longer time.
I don't know that every shooter needs to become a nurse, doctor or paramedic, but if you find that you go shooting often, you really should consider adding some medical response training to your skill list.
I would highly recommend at bare minimum, taking a class that teaches dynamic responses to stop hemorrhage. The type of class where you're stopping bleeding on a goat or pig. As gruesome as this sounds, the pig or goat suffers for a very real cause: to save lives. Usually, there's a BBQ at the end too. These types of courses are usually 4-16 hours long. These are usually through private organizations - many of them are shooting schools, and generally a certificate of training at the end is for your own enrichment.
Beyond that, the first level of EMS is called Emergency Medical Responder (which used to be called "first responder", and may still be called that in some states). It is generally a 40 hour course covering all of the very basic skills needed to support life in most situations until help can arrive. These courses can usually be found by private organizations, but occasionally at a community college.
Another option would be to take a Wilderness First Responder course. This is the first 40 hours of the EMR course usually followed by 40 hours of teaching you how to improvise and think like a person who may need to improvise. These are usually taught in a long, outdoor one-week format through backpacking and outdoors companies.
An EMT course is generally 120-180 hours long, it is the first level of EMS that is a little more "official" meaning, you could actually work in a hospital or in an ambulance if you wanted to. This covers everything that is considered "basic life support" (usually not using multiple drug types, IVs etc...usually non-surgical, non-invasive) at the most in-depth level. This type of course is usually offered at most community colleges, some universities and some private companies.
The longer you shoot and the more rounds you put downrange, the more likely you are to have or see an accident, despite how "safe" you may be. Please consider preparing yourself to deal with a medical injury. You might be the only person around to save someone's life!