Principal Gallo is an older man trying to discover which of his students terrorized his school with a prank. He appears in "Bag Man".
After an explosion went off, Principal Gallo panicked and activated the school's new security system, which automatically sent out text messages to every parent and called the police. This landed him in hot water when it turned out to be a simple prank, and with no clear culprit and higher-ups breathing down his neck, he had no choice but to detain a swathe of likely suspects and hold them until the real culprit revealed themselves.
Naturally, the suspects Sam, Jax, Gabbi, Winton, and Zee detested this, but none of them would reveal the culprit. In response, Gallo took their phones and left them — only for Jax to go missing. Angered and unable to find him, Gallo suspended him on the spot and locked everyone else in the classroom to prevent further issues, leaving a bad he found in the hallway in with them. He then left to call Jax's parents.
Later, the fire alarm suddenly went off, and when he checked the camera to their classroom he noticed that Jax's severed head was on the floor, and the other students were screaming in terror trying to escape from a strange chalk-white man in a black suit closing in on them. Panicking, Gallo once again activatesdthe new security system, summoning the authorities, but also locking down every door in the school. Realizing that he just trapped the students inside, Gallo tried to disengage the security system, but to no avail. He then tried to leave his office to rescue them, but found he could not get out either — he screamed in futile panic for someone to help them as the students were killed.