I have no desire to use this tragic incident to disparage decent people who might occasionally make a mistake. They're human and humans sometimes make mistakes.
The solution here is to not leave your gun in a bag and move away from it; to always keep your gun on your person and under your 'positive control'.
There are deaths caused by accidents and deaths caused by ignorance. Think about how that 2 year old will go through life from now on. Also, don't lose sight of the ever growing number of Americans arming themselves in the name of protection. My conceal carry program was quite easy to pass and I was stunned at the ineptness of some of the people on the gun range. The ones that never have so much as held a pistol were reason to consider getting the hell out of there until they were done. Now, in Texas one does not have to re-qualify at the range ever and I don't agree with that.