Something has totally rattled your son or the ex-girlfriend or both. Their age, relationship experience, family relationships and emotional maturity play so much of a role as does your response. Is there the possibility of a baby to worry about between the two?
Leaving a relationship on speaking terms are the actions of a more mature person. Make this relationship a learning experience, try to understand what went wrong and not let it happen again. You choose your path to this...therapist, lawyer, perhaps a very trusted religious leader you have known forever or police.
The major exception to leaving on speaking terms is someone who does something violent or someone warns you after you have been introduced by them...protecting yourself by leaving is fine...preferably find this out while dating or friends instead of married and having to deal with each other through the attorney.
I would say the restraining order is a waste of time for now.
If you won't allow her or him to properly explain things to each other or neither one will talk to one another, it's very problematic...especially when there is a baby that resulted from that 6 months together.
Don't even consider meeting someone online, through friends, church, work, school etc as okay. Unokay people are everywhere. Some are only unokay in certain situations anyway or so desperate/messed up, they cannot make a decision.