My 4 year old is getting bullied at school !

Hey lady's, I need some mom advice! Since my daughter started preschool she loved it and was excited to meet new friends and play all day loll. For the past 3 months I notice that there's a lil boy who is always picking on her or saying things like (I don't want you sitting next to me) 
First situation occurred when I dropped her off to school, she took off her jacket and accidentally brushed it over his head, he was furious and started pulling on her jacket plus yelling at her don't hit me with your jacket. I seen everything happened and I calmly said to my daughter (I know it was a accident and did you apologize to him?) so the teacher gets involved, now she's taking control of the situation of course it's her classroom. The teacher spoke to the lil boy and told him it was a accident and she did not mean to do it. she's trying to apologize to you! Can you please look at her so you can see? She repeated herself 3 times, He finally looks at my daughter and she said sorry. SMH I took my daughter to the side, hey baby girl you didn't do anything wrong but I am happy that you apologized.( hugs and kisses see you later)
Me: I went into my car called my sister n law and spoke to her because I was very upset and just started to cry. I felt helpless and It was a innocent situation... all I wanted to do is protect my daughter from this little boy with so much anger
Second time took her to school. He didn't want her to sit next to him so he yelled at her ! This time I stared right at him and he immediately put his head down. Looking at her side view ugh Me: is he having a bad morning? Teacher: yes he is Me: hey baby girl come play with the girls and let's leave Mr. Grump alone.
 Third time dropped her off and she sit on the right side and he's on the left in the back and he yells at her don't sit next to me ! My daughter class mates yelled at him and said (stop yelling at her and you mad because she don't like you) I was so shocked to see how the other kids stand up for my daughter. That shows me that he's always picking on her and being very mean.
Forth time this morning, he's sitting in front with the teacher with two other little girl. I said hi GM, my daughter sits down for story time. He turns around behind him to Tell my daughter don't sit next to me with anger in his voice. I had enough of him bullying !! So I went to the office and spoke to one of the ladies about everything that's going on. I was told that she will speak to the teacher about the situation. 
I feel so helpless for our 4 year old and my husband is so calm. I am stressing that the school does nothing about it and afraid that I may lose my cool. I have never been in this situation before. I never had too. We moved from ny to tn. It's very stressful dealing with this situation. Need some advice badly ladies. 😔