The Milwaukee girl was shot in May, while playing with her sister outside Clarke Street School. Men were engaged in a gunfight across the playground.
Sierra died early Sunday.
Several hundred people gathered at dusk on Monday at the playground near 28th and Clarke, to offer prayers for the 10-year-old and her family. Some who took part released dozens of pink and yellow balloons while others held lighted candles.
Leaders took turns speaking into a bullhorn and implored people to stop using guns to solve disputes. "With guns, it's final. There is no going back," said Kenneth Robinson, a friend of the Guyton family.
Two men have been charged in connection with the girl's death.