COLLEGE PARK, Ga. (AP) -- Cory Green stood over his nephew's coffin and asked the hundreds of mourners gathered to touch one another and repeat after him.

"If I am not a part of the solution, then I am part of the problem," Green said, the audience reciting his words. "Because I am my brother's keeper."

Family members and friends remembered Green's nephew Bobby Tillman on Saturday as a smiling, happy peacemaker and vowed not to let the 18-year-old's death be in vain. Tillman died last Sunday after a random attack at a house party. Investigators say he was stomped, kicked and punched to death.

About 200 people gathered to remember Tillman at Siloam Church International in College Park, south of Atlanta, consoling each other in the pews as they were told to honor Tillman's life and example by standing up for themselves and others.

"What happened on the 7th made no sense," said the Rev. Olu Brown of Impact Church in Atlanta, referring to Bobby's death. "It still today doesn't make sense. I don't know if we will ever see a day in our lifetime when it will make sense."

Brown urged the audience, especially the crowd of Tillman's young peers, to honor his example in their own lives.

"Don't you get down because Bobby died," Brown said. "Bobby's life cannot be a period in your destiny. You've got to take Bobby's 18 years and fold them into your story. ... In 18 years, Bobby finished the job."

Police say Tillman, who did not know his attackers, became a target after a fight broke out among people at a party in the Atlanta suburb of Douglasville. Investigators say the fight started when a woman hit a man. The man said he would not hit the woman back but vowed to hit the next man who walked by.

Four men have been charged with murder in Tillman's death. In the days since, his mother, Monique Rivarde, has been outspoken on the issue of youth violence.

At the 2-hour funeral service for Tillman, the focus was on his life. Many wept as images of Tillman's smiling face were flashed across a screen in a tribute featuring past birthdays, Christmases, special occasions and everyday moments. Among those paying tribute to Tillman was his high school choir.

Tillman spent most of his life in the Los Angeles area, then moved to Georgia after his sophomore year of high school. He graduated from Chapel Hill High School in Douglasville.

Tillman was enrolled at Georgia Perimeter College, and his passion for basketball fueled his dreams of becoming a sports agent.