Whether or not firearms are used in suicides is a minor point. If someone want to kill themselves, there are plenty of readily available options aside from firearms. That's why, when it comes to "gun violence," most realists completely exclude suicides from the statistics.
I almost think we’d be better off giving this to them. If they can prevent suicides thats 2/3 the gun deaths. Also if the general public knows 2/3 are suicides it might change their mind on gun control. Who knows but I doubt this group has any good intentions knowing their track record.