In a tweet late Friday, the Sheriff's Office said one person died and two were injured after a game played between host William M. Raines High School and Robert E. Lee High School.
The Sheriff's Office said early Saturday that one male and one female were shot and transported to hospitals, while one young male was pronounced dead at the scene.
The victims’ names had not been released as of early Saturday.
Deputies estimated that 4,000 people attended the game, which was the season opener for Raines. Around 3,000 fans had left by the time the shooting began, the Sheriff’s Office said.
"With the amount of people there, we should have many witnesses," a sheriff’s spokesman said.
There were several fights and disturbances during the football game, according to the Sheriff’s Office, and officials said they will be looking into those to see if there are any connections to the shooting.
Deputies said the shooting occurred up and down the sidewalk -- between the stadium and the school entrance -- around 10 p.m. Officers at the scene found three victims with gunshot wounds. One victim, a young adult male, died at the scene. Rescue transported two others to the hospital.
Federal authorities are assisting JSO in the investigation. A search is on for a single shooter, authorities said.
Duval County Superintendent Diana Greene said officials were still in the process of gathering information and will release a statement later.
Greene did say, however, that the incident was a “very troubling reflection” of what's happening in the Jacksonville community.
This is not the first time there has been an incident at a football game between the two schools.
A 20-year-old was shot after a 2012 game at Raines High School.
This is a developing story.