reporter: he was under investigation in massachusetts for buying firearms and gun friendly new hampshire which doesn t require background checks or licensing and keeps no record of sales. authorities suspected christoph was selling fire arms in massachusetts which has tough gun laws. those weapons that are community guns were sold off to other potential perpetrators whether they are involved in gangs or commit other crimes. guns also slip into massachusetts from nearby maine and vermont where a license isn t required for gun purchases. over two-thirds of those crimes were committed with guns that were bought from outside of our state, not even from within our state which is especially concerning. reporter: gun control has become a war between the states. since newtown, at least six state legislatures have passed tougher gun control measures, more states have acted to weaken gun laws and a couple have done both. in washington, d.c., the nation s capital, they re tough on guns.
some people said as many as 20,000. is one more law really the answer? joe johns has an outfront investigation. reporter: 21-year-old matthew christoph was killed by police after he shot a summerville, massachusetts, detective at point blank range through the window of a car november of 2010. the mayor still remembers the day vividly. the calls and i said one of the calls you never want to get. an officer was shot. reporter: he was under investigation in massachusetts for buying firearms and gun friendly new hampshire which doesn t require background checks or licensing and keeps no record of sales. authorities suspected christoph was selling fire arms in massachusetts which has tough gun laws. those weapons that are community guns were sold off to other potential perpetrators whether they are involved in gangs or commit other crimes. guns also slip into massachusetts from nearby maine and vermont where a license isn t required for gun purchases. over two-thirds of those