My friend (Let's call her Emma) hurt my other best friend (Daniel) on purpose and now he wants me to not be friends with her. Here's what happened. Emma, Daniel, and I were in the band room waiting for the bell to ring when I told Daniel to stop doing something and he put his forehead against the wall. As he moves back to talk, Emma tells him to put his head back and that she wants to try something. He walks back over and puts his band binder on top of his head then his forehead on the brick wall. Suddenly, Emma pushes the back of his head against the wall, closing whatever gap was there before hand. He moves his head back and starts yelling at Emma. His face was red and pink and he walked off to the back of the room. Emma tries to follow him to tell him that He's fine and that it didn't hurt that bad. Luckily, I pulled her back and sent her to the front of the room away from him. I walked over to check on him (as Emma and him don't trust each other and don't get along well). He let me check for any bumps or lumps on his forehead, luckily there were none. A few minutes later the teacher noticed and walked over to check on Daniel. Daniel and I told him the story and Emma shouted from across the room "I did not". I gave her the death glare and she walked off as the bell started ringing. I let her walk off and waited for him. He stomped off angrily and said he didn't want to talk to me or Emma right now. Later that day Emma walked home with me and started talking about how "She wasn't to blame because she didn't know that it would hurt him." This pissed me off and I started walking faster and she didn't take a hint. It happened on a Friday and I didn't get to see him or her over the weekend, and on Monday he said that he wanted me to not be friends with Emma anymore. I said I would think about it and asked him why he was mad at me though. He said he felt like I didn't do anything to help and that I was just standing there as a witness. This ticked me off because he knew I helped and separated her from him. I tried distancing myself from Emma but she was like a leech. She wouldn't leave my side. The only time I would escape from her was in my 4 core classes and art but even in art class she was still in the room trying to bug me. She wouldn't take any hints either. Now he brings it up from time to time but I feel like the a**hole for not doing anything immediately. At first I knew that her birthday was coming up in a few days and I didn't want to make things super awkward. It's been about a month now and I feel like I'll just be a dick for bringing it up this late, but it still chips away at me knowing that I should have done something.

Am I the a**hole and what should I do?