Mass shootings versus the Second Amendment

Using as examples cases of mass shootings in America perpetrated the last 25 years, answer the following questions:
1-What role do interest groups like the NRA play in this complex and divisive national debate?
2-Which other factors play a significant role in the complexity of this issue and why?
http://www.youtube.com/watch?v=32CiOoyHXNI
http://www.youtube.com/watch?v=Jt510ljRxVo