(CBS) — Friends, classmates and family filled a West Side church Saturday to remember Demetrius Griffin — the 15-year-old Steinmetz High School student who was murdered by a gunshot wound to the head and set on fire in an Austin alley last month.

The service, at the New Mount Pilgrim Missionary Baptist Church, opened with a declaration by the Stars of Heaven singers that “Chicago is in need of help.”

READ MORE: Jussie Smollett Takes The Stand At His Disorderly Conduct Trial

Brunson Math and Science Academy Principal Carol Wilson said until he graduated in June, Demetrius was everything from assembly set-up manager to distribution manager.

READ MORE: Sharon Gless On Book 'Apparently There Were Complaints: Cagney & Lacey 'Changed The History Of Television For Women'

Wilson had to compose herself as she told attendees she had imagined many times Demetrius would grow up to become a stagehand and eventually the stage manager for a major Chicago theater.

“Demetrius mattered,” said New Mount Pilgrim’s pastor, the Rev. Marshall Hatch.

MORE NEWS: Chicago Weather: Colder Temps Blow In This Week

Speakers called on those who know who killed him to turn in the killer. The Leaders’ Network ministers have offered a $2,500 reward for information that leads to the arrest and conviction of the killer.