For non-rescue personnel (the rest of us), it looks like the best thing you can do is simply make sure that nobody gets closer than 150 feet. If you're certain that aerials are deployed, you can approach (from the FRONT/pointy-end) and knock five or more times. One or no knocks means that you need to phone the authorities after retreating to a safe distance - there is nothing that you can do for them (special tools are needed to crack it open).