Cop: We're here to arrest your kid.
Mom: I want to see the warrant
Cop: You're under arrest.
In which case, yeah, the cop is in the wrong. Or it could have been.....
Cop: We're here to arrest your kid.
Mom: I want to see the warrant.
Cop: It's an arrest warrant, ma'am, and we don't need to have it with us to show you. But you can come down to the station and everything can be explained then.
Mom: You aren't taking my kid!
Cop: Ma'am, we really don't need your permission here. Please let us do our job. You'll be able to see your son down at the station and we can sort it all out there.
Mom: No!
Cop: Ok. Well, I'm sorry to do this, but you're under arrest.
In which case, the cop is just doing his job. Yes, I know there is an issue with there not having actually been a warrant at that time, but the officer may not have known that and was acting in good faith.
So while y'all are
, we still don't have enough information to go on.