Sylv is a Hispanic high school senior who lives on a farm where she helps care for her chronically ill mother. She is a high-achieving student who has secretly earned acceptance to Brown University, a fact she hides to avoid hurting Autumn's feelings. Her deep empathy and quiet strength surface as the terrifying events in the auditorium unfold, driving her to protect the people she loves.

Autumn is a high school senior whose greatest ambition is to attend Juilliard and become a professional ballerina, following the path of her late mother. She deeply misses her mother and struggles with a home life that has deteriorated under her father's alcoholism and her brother's mounting anger. Her relationship with Sylv provides her with a vital sense of safety, allowing her to hold onto her dreams of leaving Opportunity, Alabama.

Tomas is Sylv's twin brother and the self-proclaimed bad boy of Opportunity High School. Underneath his rebellious reputation and history of school pranks, he is fiercely protective of his sister and deeply loyal to his friends. He operates with a reckless energy but possesses an underlying desire to redeem his reputation and protect those unable to protect themselves.

Claire is a senior track runner and ROTC member who comes from a military family. She originally feels glad to be outside during the assembly, but her relief shatters when she hears gunshots. She struggles with intense feelings of guilt over her past relationship with Tyler and feels a heavy responsibility to protect her younger brother, Matt, who is trapped inside.

Tyler is a former student who dropped out of Opportunity High School following a string of violent altercations. He possesses high intelligence, evidenced by his excellent SAT scores, but his life unraveled following the tragic death of his mother. Consumed by grief and a deep sense of abandonment, he returns to the school to enact revenge on the community he feels cast him aside.

Fareed is the only Muslim student at Opportunity High and serves as Tomas's most trusted confidant. He demonstrates remarkable composure and clear-headedness when chaos erupts in the school. He acts as a practical voice of reason, balancing Tomas's impulsive nature with steady, actionable planning.

Chris is a member of the high school track team who provides a stabilizing presence for Claire. He offers practical support and logic when the crisis unfolds, taking charge of contacting authorities. He provides a grounded perspective when Claire begins spiraling into self-blame.

Matt is Claire's intelligent, gentle younger brother who suffers from lupus. He is known for his compassion and his fascination with astronomy. His vulnerable position inside the auditorium causes immense panic for his sister outside.

Principal Trenton is the head administrator at Opportunity High School. She leads the morning assembly and is the first authority figure to realize the severity of the threat when the auditorium doors are sealed.

Mr. Browne is the father of Autumn and Tyler. Following the tragic car accident that killed his wife, he turns to alcohol to cope with his grief, completely fracturing the family dynamic and leaving his children to fend for themselves emotionally and physically.

The late mother of Autumn and Tyler, she was once a principal ballerina for the Royal Ballet. Her death in an exhaustion-related car accident serves as the catalyst for the Browne family's collapse and leaves a lasting impact on her children's lives.

The mother of Sylv and Tomas. She suffers from a chronic illness that requires constant care from her daughter. She relies on her children and shares rich family stories to keep them connected to their heritage.

The grandfather of Sylv and Tomas. He shares traditional stories of brujería and life lessons with his grandchildren, providing them with a strong sense of cultural identity and familial grounding.

Deputy Lee is a law enforcement officer who responds to the crisis at Opportunity High School. He attempts to gather information from Claire and Chris to understand the motivations of the attacker inside the building.

Kevin is known as one of the only out-and-proud gay students at Opportunity High. He is confident in his identity and previously recited a Harvey Milk speech during history class, drawing Tyler's targeted ire.

Asha is a student in the auditorium who gets caught up in the panic. She fiercely tries to protect her younger sister, Nyah, when the situation escalates, drawing the attention of those around her.

Nyah is Asha's younger sister. Her vulnerable presence in the auditorium heightens the danger and prompts others to step in to protect her from harm.

Jonah is the school security guard. He is known for his kindness, having previously gone out of his way to offer comfort and assistance to Claire when her brother was hospitalized.

Coach Jameson is an athletic coach at Opportunity High who helps organize community events for the students. He is present in the auditorium during the assembly when the crisis begins.

Steve is a junior at Opportunity High who becomes immobilized by fear during the crisis. He relies entirely on direction from his peers, specifically Sylv, to find his way toward an exit.

CJ is a student at the high school and a friend of Steve Jackson. Their unknown status during the lockdown remains a major point of anxiety for the students waiting outside.

Mei is a student who skipped school on the day of the spring semester assembly. She uses her blog to process the horrifying events and spread information as fragmented news reaches the outside world.

Trace is Claire's older sister who enlisted in the military. Claire frequently compares her own response to danger to Trace's rigorous training and service, viewing her sister as the ultimate standard for bravery.