Jaelynn Willey, a 16-year-old student at Great Mills High School in St. Mary's County, died Thursday after her family took her off life support.
On Saturday, her classmates participated in the march in Washington D.C.
"I got a text that morning saying you should check up on your sister, there has been a shooting at the school," said Great Mills graduate Jillian Carty.
"Our principal got on the PA system and he said, 'We are on lockdown. Clear the hallways,'" sophomore student Saar Shah recalled.
"Everyone was just overwhelmed and shocked that it would happen in a community like ours," said Allison Pugay.
In the massive crowd, you could spot them by their gold and green. Members of the Great Mills community wore their high school's colors in solidarity at the march.
"I think our group consisted of about 250 people," said Emerson Schaeffer, a Great Mills graduate who helped organize their group's presence at the D.C. rally.
Some had been planning to march before Tuesday's shooting.
"You never think it's going to happen to you until it does," said Shah.
That is when their school became the latest to become a crime scene. Police said 17-year-old Austin Rollins showed up with his father's gun and shot his Willey, his ex-girlfriend, and 14-year-old Desmond Barnes, another student at Great Mills who survived the shooting.
Barnes was wounded in the leg, but was released from the hospital a day after the shooting. However, Willey was determined to be brain dead and was taken off life support two days after she was shot in the head, her family said.
"She was just a happy person," said Shah.
"I'm just here to memorialize her and to tell her story to any strangers that ask," said Pugay.
They brought their story and their voices by joining with hundreds of thousands of other young people from across the country.
"This is a revolutionary event," said Schaeffer.
While the March for Our Lives can't change what happened at their school, students past and present said they leave with hope there will be change.
"With this kind of support, we can really make a difference," said Shah.
"There is hope," said Pugay. "I just want people to know that even though times seem very rough right now, especially in my community, that change coming."