It could be any number of things from a hormonal imbalance to needing more structure or needing help learning anger control.
My niece when she was little she had temper tantrums where she would get so mad she'd turn purple, pass out, or beat her head into the floor.
Three child psychologists later, basically she got mad and had trouble getting unmad. Once she got angry, she didn't know how to self-sooth and calm herself down. Her dad's family, we found out later, had similar explosive tempers. We just had to break her mid-cycle before she got carried away. Let's say the cure involved a squirt gun and three very embarrassing years.
But at 25 she's still dramatic but no more temper tantrums where she hurts herself. She's married and had two kids of her own.
Don't be afraid to reach out to a child psychologist. Sometimes its something as simple as teaching a kid how to control and let go of their anger. And if is hormonal, they can help you with that too.
You need to find out the 'why' of the temper before you can fix it. Environmental, hormonal, or emotional. Once you know why, you can can develop strategies to control it.