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At this point, his recourse would be to file for a Temporary Restraining Order TRO. He would need to get a copy of the police report and then contact the district attorney to file the petition. The TRO would be granted due to the assault and is normally in effect for a few weeks before a Permanent Restraining Order hearing can be held to issue one permanently.
Once one is issued, the boyfriend would be prohibited from having any contact with your son and if he showed up at a location where your son is, your son can call the police who will then charge boyfriend with criminal violation of a retstraining order.
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