People mourn at the Frankfurt main station in Frankfurt, Germany, on Aug. 5, 2019. An 8-year-old boy was killed by a moving train after he and his mother were allegedly pushed by a man onto the tracks on July 29 at the Frankfurt main station. (Xinhua/Lu Yang)

People mourn at the Frankfurt main station in Frankfurt, Germany, on Aug. 5, 2019. An 8-year-old boy was killed by a moving train after he and his mother were allegedly pushed by a man onto the tracks on July 29 at the Frankfurt main station. (Xinhua/Lu Yang)

People mourn at the Frankfurt main station in Frankfurt, Germany, on Aug. 5, 2019. An 8-year-old boy was killed by a moving train after he and his mother were allegedly pushed by a man onto the tracks on July 29 at the Frankfurt main station. (Xinhua/Lu Yang)

A mourner presents a flower to offer condolence at the Frankfurt main station in Frankfurt, Germany, on Aug. 5, 2019. An 8-year-old boy was killed by a moving train after he and his mother were allegedly pushed by a man onto the tracks on July 29 at the Frankfurt main station. (Xinhua/Lu Yang)

People mourn at the Frankfurt main station in Frankfurt, Germany, on Aug. 5, 2019. An 8-year-old boy was killed by a moving train after he and his mother were allegedly pushed by a man onto the tracks on July 29 at the Frankfurt main station. (Xinhua/Lu Yang)