PHOTOS: Hundreds of students rally to remember slain 17-year-old, demand end to gun violence

Last Friday was the last time Ryan Dela Cruz's classmates saw the 17-year-old student alive.

This morning, his friends stood huddled on the Franklin High School football field, grasping one another in a moment of silence.

Around them, hundreds of students wore orange t-shirts reading #KeeptheSouthEndSafe in a call to end gun violence. Dela Cruz, an aspiring Marine just two weeks shy of graduating, was at least the sixth teenager killed by gun violence in King County this year. Read More: Fatal gun violence looks different for Seattle kids, depending on where they live 

Letrell Paris, 18, remembered meeting his friend Dela Cruz in the sixth grade, playing frisbee at lunch, and riding their bikes downtown on summer break.

"I don’t know why, but I kept expecting to go to school [today] and see Ryan standing there with a big smile on his face," he said. "It feels so unreal."

Paris said he never would have expected Dela Cruz to become a victim of gun violence. 

"He was a very whole-hearted person," Paris said. "He liked to help others all the time. I think that’s one of the reasons he wanted to be a Marine."Read More: Immigrant moms in SeaTac prison 'could hear their children screaming' 

Police reported that Dela Cruz left his home last Friday with friends to go try and spot ghosts in a popular park for "ghost hunting" when they encountered another group of people. Shots were fired, police said, and Dela Cruz was killed.

On Friday morning, Franklin High School students attended an assembly in remembrance of Dela Cruz. Local activist Nikkita Oliver spoke.

"Gun violence has become business as usual for us," she said. "And what happens is our community tends to keep going and accept the trauma."

But Oliver stressed the importance of the leadership of Dela Cruz's classmates in the ongoing discussion on gun violence. In the wake of mass shootings, she said, plenty of students have spoken up, but "they don't all look like you, or come from where you come from."

"So what you do today is incredibly important for our community," she said.

After the assembly, hundreds of Dela Cruz's classmates rallied, chanted, and carried signs outside Franklin High School on Rainier Avenue South.

They then gathered on the football field, where Dela Cruz's friends hugged one another in a circle and held onto a white balloon.

The group released the balloon: It flew up, away from the high school, and disappeared into the clouds.