The Thunder Heads were first seen and mentioned in the arc "Building Bridges".
The Thunder Heads, are a ruthless street gang. During the events of the "Building Bridges" arc, a lot of street violence and assaults were happening to students attending Zora Neale Hurston Middle School. It wasn't proven, but they may have been responsible for some of the muggings and the assaults.
They are a group of teenage boys around 12 to 16 years old. Each of the members has a symbol on their jacket. The symbol is like a combination of a capital T and a small h combined into one.
Usually most of these boys come from Hispanic or Latino families. And most of them are either poor or have unhappy lives. Therefore they form together as a selective group, who are tough and look out for each other at all costs. Also it is known that they do steal, but it is unknown to what extent. They do not kill people, but they do beat people up and possibly take part in gang beatings.
Also a lot of the members in this gang are known to move onto "The Risers" when they get older. This is believed to be a much more serious and violent street gang. A gang in which members can actually get harmed or killed. Or harm or killers rival gang members.
About two to three months prior to the events of the arc, Victor Torres reluctantly quit their gang and transferred to Hurston Middle School. The reason he quit, was because his older brother Quincy was a gang member of The Risers. Then six months earlier during a rumble, Quincy was shot in the back by a rival gang member and paralyzed for life. Victor's mother was worried that he would eventually move onto the Risers too. So Victor quit and the gang became very mad at him.
Then later on, someone begun vandalizing and trashing the inside of Hurston Middle School. The gang was suspected of doing it, because their symbol was being used in some of the graffiti. But it was proven that their grudge against Victor was personal. So they would only come after him, not his new school. Then it was eventually proven that it was being done by fellow Hurston Student Tony Boyd.