Remember, under MGL any property worth more than $3 must be turned over to the local PD and becomes the property of the founder if not claimed within a specific time (I think it's 30 days).
Chances are a found handgun would be worth more than $3.
And I am 100% certain that in MA, there is NO WAY IN HELL that any LE agency would turn over a gun found if not claimed (and not involved in a crime) after any period of time. It's hard enough to get them to return a lost/stolen/confiscated gun to the KNOWN owner in this state! In other words, they would gleefully ignore said law (like they ignore many others that they don't particularly like).
I'd like to say just pick it up, make it safe, and bring it in.
But in today's Massachusetts I doubt that is a wise course of action.
Very unwise, see below.
There was a shooting down the street that night. The guy shot twice at another dude but missed.
Probably the same one used in the shooting
If your prints are on it, you also become a suspect. No thank you. I'll call it in and otherwise not touch it . . . even if I don't know that it might have been a crime gun.