When James Eagan Holmes shot and killed 12 people in an Aurora, Colorado, movie theater in 2012, one of the weapons he used was an AR-15-style rifle manufactured in Massachusetts. The Bay State has banned civilians from purchasing or owning assault weapons and high-capacity magazines for decades, but companies like Smith & Wesson, headquartered in Springfield, can still build them here and sell them elsewhere. Backed by parents who lost children to mass shootings and the Stop Handgun Violence organization, a group of Democratic lawmakers launched an effort Tuesday to change that dynamic, filing legislation that would extend the existing assault weapon ban to cover their manufacture for civilian use as well.