Police said a school resource officer discovered the weapon after responding to the altercation. The officer and school staff broke up the fight and learned that one of the students had a gun.
Cpl. Raushan Rich of the Delaware State Police said the presence of school resource officers helped prevent the situation from becoming more serious.
"Thankfully, we do have the school resource officers who were right here and on site and able to take quick action to prevent anything from escalating," Rich said.
According to Rich, the investigation led to a search of the student's backpack.
"The SRO learned that the student had marijuana in his bookbag, so during the subsequent search of the bookbag, the SRO recovered a small quantity of marijuana as well as a loaded handgun," Rich said.
Police said the student was taken to a hospital for injuries suffered during the fight. After receiving treatment, the student was arrested and charged with multiple felony gun offenses.
Classes were not in session Tuesday because of the state primary. However, the Christiana School District provided a statement describing the incident as unacceptable and praising the response by school and law enforcement personnel.
"The swift and coordinated response of our SRO, school staff, and Delaware State Police is exactly what our safety protocols are designed to produce. That response kept our students and staff safe," the statement said.
Police said they were relieved the situation did not escalate further.
"Thankfully, we were on site and able to prevent any tragedies from taking place and hopefully this is a message to anyone else thinking of bringing a firearm to school," Rich said.
The student is being held on $87,000 bail.