He is a nice little boy, but has no language skills and is very aggressive.
From what you have said, it doesn't sound like the "nice little boy" appears very often. When is he this nice little boy?
The fact that he has no language skills is a huge warning signal to me. What does this mean in practical terms? Does he simply not speak, does he use single words (e.g. yes, no, more) or is he using simple sentences, but not at the level of a two year old. A six year old boy who cannot speak needs outside help. If he's in school, he might be able to get help through the school-- if he's not already.
I do not necessarily associate violence at this age with something inherently wonky in the child. It sounds like he's learned that tantrums pay off-- this is a six year old having two-year-old-style tantrums. Because he's so big, it's become dangerous. (If you want to have him around, I would suggest taking the other children out that day. He might benefit simply from having one-on-one with an adult to show him how to be.)