17-year-old Great Mills High student Andrew Wyatt Rollins opened fire on other students in a school hallway yesterday, New Zealand time.
16-year-old Jaelynn Willey is in critical condition in hospital and 14-year-old Desmond Barnes is in a stable condition.
"Everyone feels so disheartened because so many shootings have happened and no decisive action has been taken to stop them," fellow Great Mills High student Mikayla Miles said.
She said students were "crying, scared and fearing for their lives" during the lockdown.
"I don't wish this upon anybody else," she said. "No parent should send their kids to school worried they might not come back.
"There's just no excuse for how this happened - at the end of the day these are kids' lives. Obviously our system isn't working at all and something needs to change."
Great Mills High School is closed until April 2.
Mikayla Miles said representatives of the school would join the March for Our Lives on Washington DC in a protest against gun violence in schools on March 24.