No other information about where the weapon was found has been released. Police have said that information is confidential at this time.
The search for the .32 caliber semi-automatic pistol had been going on since last week, when investigators believed the suspect discarded it after leaving the high school campus.
Cesar Cortes, 19, was shot and killed last Tuesday.
According to sources with knowledge of the case, three students went to a storage area of Bellaire High School Tuesday afternoon, because the alleged shooter wanted to show the two other teens his gun.
One teenager then walked away from the storage area. That's when he heard a shot.
Sources say the 16-year-old suspect then carried Cortes out of the storage area before running away.
Friday morning, a judge ruled that the Bellaire High School student charged with manslaughter in Cortes' shooting death will remain in custody for now.
The 16-year-old suspect was brought into court in handcuffs for a hearing. His mother was in the courtroom and broke into tears as the teen was led into the room.
Defense attorneys said the boy should be released to his mother, claiming he will be supervised and had never been in trouble in the past. The prosecutor countered by saying the teen could be a danger to himself or others.
The judge agreed and, for now, the teen will stay in juvenile detention.
Eyewitness News has learned there may have been a previous incident involving a different student at Bellaire High School prior to the shooting. Prosecutors want to know more about that prior incident.
As the teen's mother left the courtroom, tears streamed down her face.
ABC13's Miya Shay reports
Friday afternoon, friends and supporters of Cortes gathered for two events to demand change.
Just after school, at least one hundred students chanted "Justice for Cesar" while holding up homemade signs in a school courtyard. The rally was organized by the Bellaire High School chapter of Students Demand Action, a gun safety activist group.
RELATED: Bellaire HS shooting suspect carried victim out of building after shooting
"We decided that having a Students Demand Action chapter here is important," said Izzy Richards, founder of the group. "We are at risk as students, and we are at risk as people who care about the politics of this situation, and are addressing it on a larger scale."
After the rally at the school, students then drove to HISD headquarters on Houston's north side to hold a silent sit-in. Several Houston members of Moms Demand Action were also present.
There were tears, songs, and above it all, a message to HISD administrators the students hope they will hear.
TED OBERG INVESTIGATES: Bellaire High first U.S. school shooting fatality in 2020
"We need a lot of help, we need the adults in the room to support us," said Richards.
Multiple students have told ABC13 that they feel administrators are not listening to the needs of principals and students at the school level.
Since the shooting, Interim Superintendent Grenita Lathan has refused to answer any questions. On Friday, Lathan would only speak to the media at an MLK oratory competition if no questions about Bellaire High School were asked.
"I didn't know Cesar, but I'm here (at the rally) today because this isn't fair," said student Bianny Perez. "This isn't the first time that something happened at Bellaire HS, and they did nothing about it. And something needs to be done."
A celebration of life service was held for Cortes on Saturday.
SEE ALSO: Brother of Bellaire HS shooting victim gives emotional speech at vigil