Siswanto was born in 1963 and lived without a home, moving between Jakarta and Central Java and supporting himself by begging and casual work.
Between 1994 and 1996 he approached boys living on the streets, offering food, money or a place to sleep, and killed twelve of them, stabbing and mutilating the bodies. The victims were children whose absence produced no report, which is why the killings continued for two years.
He was arrested on August 6, 1996 while begging at the Tegal railway station in Central Java, and confessed.
He was sentenced to death on May 21, 1997. He was never executed and died in prison on March 26, 2007.
The nickname the Indonesian press gave him, Robot Gedek, came from his manner in custody. The accessible sourcing on the case is Indonesian press reporting and is thin on the investigation; no victim is named in anything available, which is itself a fact about who they were.