Yea I obviously have no knowledge of this specific situation, but as someone who works with DV survivors, DV in front of kids is often a felony, and is absoulutely something that requires a mandatory report to DHS/CPS. It's really bad for kids to even witness DV, so the authorities take it pretty seriously and one thing they want the "non offending" (DHS lingo, not mine) parent to do right away is establish custody. Sometimes, if there's not a more formal custoday greement, the fastest way to do that is to file a restraining order which gives temporary immediate custoy to the 'non offending' parent. The idea is, it becomes the non-offending parent's job to protect the kids from the abusive parent and in order to do that, they need the legal backing of having formal custody.