Is dash camera sound recording in a public space legal?

Per court order modification agreement, we are to drop off the children at either the other parent's home or school grounds instead. Public space was selected as an option due to prior historical behaviors which made me feel unsafe going to their residence. I pull up to the kiss and ride, immediately boyfriend approaches my vehicle, opens the car doors and hustles my boys out. He then gets confrontational with me, harasses me and threatens me all while sharing a few nice words. He shoved me against my vehicle and then laughed while walking away all while in front of the children. Both the boyfriend and the ex-wife knew they were being recorded, camera caught the sound but not the act as they knew to walk behind the dash camera to perform this act. Is this sound recording legal as I plan on using it in court when issuing a protective order against the boyfriend? I am currently trying to acquire and attorney.