"So many children out there are in gangs, and it is your job as students to say no to gangs and yes to a great future," Hadiya said in the video, produced by Digital Youth Network and posted to YouTube in 2008.
Another girl featured beside Hadiya added, "So many children in the world have died from gang violence. More than 500 children have died from being in the wrong place at the wrong time."
The Digital Youth Network program offers after-school and in-class opportunities for students to create positive messages while learning media production skills.
Hadiya's video was part of the SAVE project, which stands for Stop Abuse and Violence Everywhere.
"Her and her group decided to tackle gangs as a part of that," said Akili Lee, Digital Youth Network cofounder.
Tene Gray, the organization's director, said the surfacing of the video is "quite eerie."
"As they saw it, [gangs were] a gatweway to a lot of the violence happening then, and that, of course, was when she was in middle school," Gray said.
And Hadiya's message may now be more powerful than ever.
"It's beyond ironic but really tragic," Lee said. "Hopefully [the video] will do some good in terms in terms of spreading the message."
Hadiya's project showed how important it is for youth to have an empowered voice, said a statement on Digital Youth Network's website Thursday.
"Hadiya shined her light on us here at the Digital Youth Network as a student, a learner and a creative voice," it said. "...We are inspired by the passion Hadiya and the youth of Chicago have shown for sculpting a better future for themselves and others."
Just a week earlier, Hadiya had performed at Obama's inauguration with the high school band as a majorette dancer. She was also on the volleyball team at King.
Hadiya was in the wrong place at the wrong time, police and friends said. But true to her warning, she stayed out of gangs, police said.
In an initial police statement, police said someone in the girl's group may have been involved in gangs, but Chicago Police Supt. Garry McCarthy later said there was "no indication" that Hadiya or anyone else had gang ties.
Police and a witness, a friend of Hadiya's, said a gunman jumped a fence, approached the group and opened fire. Three in the group were shot as they ran, police and witnesses said. Her friend said the group was mainly made up of marching band members and at least one member of the volleyball team.
Hadiya was taken to Comer Children's Hospital, where she died less than an hour later.
Police said in the statement that the gunman then got into a car and drove away, though McCarthy later said there might be two suspects: one shooter, and someone who might have driven a white Nissan getaway car.
"What we believe happened is that this is some sort of territory that some gang calls their own," McCarthy said.
Hadiya's father, Nathaniel Pendleton, had a message for the ones who he said "took the light of my life."
"Look at yourself and know that you took a bright person, an innocent person, a nonviolent person. This kid didn't like violence at all," he said.
"She was destined for great things, and you stripped that from her."
Police are offering a $14,000 reward for information that leads to the arrest of her killer, who was still on the loose Thursday morning.