What can I do to help my dog's aggression?

I'm sorry this happened! I think it depends on what happened prior to this moment and if you are noticing anything that causes this behavior to replicate. If you could identify the trigger (any thing that causes you dog to increase their awareness, fear, or reactivity) then you have a solid ground of how to help them. Other than maybe getting help from a dog trainer, I'd recommend a vet visit as well to make sure there is nothing medically wrong with your dog that might cause them to act out of character. For example, an injury or illness could cause a dog to be act out because they are not feeling well. I hope this helps and that you are healing!