The problem with gun control in MA is that legislation is addressing the wrong people. All these shootings are career criminals with illegal guns, yet gun control is aimed at licensed owners. And that's why our current gun control legislation doesn't work. Licensed owners are not the problem, so laws hindering licensed owners are useless to stop shootings like the ones OP mentioned.
That's a perception problem we need our reps to overcome with the voting public. Instead of vilifying specific weapons, capacities, and functionalities, we should be vilifying the actual villains. Jay McMahon has a great point that we're not hard enough on career criminals and traffickers (guns, drugs, people). I actually wish he stressed this part more, as it actually is one of his best pro-gun rights arguments despite not being directly about gun rights. If we could get an elected official to chase that end and actually make a change, we could prove to the voting public that restricting lawful licensed owners is the wrong method of gun control. Beating our chests over 2A rights is just not the right approach to the general public. Most will never truly understand what that means, so trying to use the constitutional argument while the general public is reading headlines about school shootings is the wrong approach. Show the public who is actually causing gun related crime in MA, show them how to stop it (or at least slow it down to lower levels), and then ease restrictions on lawful licensed citizens.