The Big Bad Wolf

Thursday I had an altercation with one of the teaching aides. Let me preface: this woman is a large (6 ft. at least 200 lbs) African American, she thinks yelling at kids is good discipline, and she also loves to argue. She is "in charge" of the lunchroom. So Thursday I was standing in the lunchroom talking to my aide when I see her yank one of my tiny 1st graders out of the lunch line. And by yank, I mean she grabbed his shirt by the collar and physically pulled him out of the line with enough force to rip part of his shirt. A few lunch staff said it looked like she choked him. He was hysterically crying so I instinctively went over to find out what happened. As I ask the student what happened, the aide comes over and tells me she's, "taking care of it." I ask her what happened, and all I heard from her was, "older kids...kiss my ass." So I ask her again, "Wait, what happened?" and she yells at me, "I already told you what happened!" So I said that I didn't hear her, could she please tell me again to clarify, and she got in my face and yelled at me, "I told you what happened. He's not special, he knows what he did!" I was livid. I sat next to him until the lunch period was over and ignored her. After lunch I went to the office to talk to the vice principal (the principal was not there) only to find that the aide had beat me to it and was putting her own spin on the situation. Of course she was. I calmly explained what happened, and my concern for the student's safety, and how she got mad at me for asking what happened. They (the two vice principals) told me that the aide is upset because "she doesn't feel supported" and she's in charge of the lunchroom. I told them I understood that she didn't feel supported because I intervened, but again said I was concerned for the student's safety. Then I asked what exactly did the student do? They told me he shook his butt at the other kids and said, "Kiss my ass" to them. Then they told me he needs to know he did something wrong. Um, yeah, no shit...which is part of my point. He's a special education 7 year old who lacks good decision making skills!
What I didn't say (because you always have to watch what you say - esp. when it's about one of the principal's buddies) is that I'd fully support her if she was disciplining him legally and I knew the reason why. All I (and most of the staff) saw was her yanking him by the shirt. I was very concerned because he could have been hurt (a tiny 1st grader) and it's illegal to use physical force on a student. If I don't stand up for him, who will? This is not the first time I and others have witnessed this woman being physical with a student. The only time I even touch the kids is if they are violently out of control and a danger to themselves and others and I try to calm them down. After school I talked to the student and his father about what happened. He was upset about what his child said, but he didn't seem to care about the aide yanking him. If the parents complained, then maybe something would get done about it. The next day the aide acted like nothing happened at all and was overly nice to me.
I am still angry about this whole incident because I feel kind of helpless. I went to the administration and as far as I know, they did not address the issue (physical force) with the aide. So what do I do? School should be a safe environment for our kids, but a person who works in the building is not safe! It's my responsibility and I want to protect the student's safety and prevent this from happening again. If I call the union or report this, I may get reprimanded (even though I did NOTHING wrong) because this aide is "in" with the principal and it'll also make the administration look bad as they did not address this issue. Then it'll probably come back to bite me in the ass.
"But you get the summers off" people say to me. Really, please walk a day in my shoes.