Johnson was born in Illinois in 1951. At nineteen he was convicted of raping a woman in Joliet and burning her with a cigarette lighter, and was sentenced to twenty-five to thirty-five years. He was released on parole in 1983.
Ten people were killed in Will and Cook counties between June and August of that year, all of it at weekends, which is what gave the case its name locally. The victims were shot or stabbed and were not connected to one another or, so far as the evidence went, to him. The worst single episode was at a ceramics shop in Joliet, where four women were shot dead.
He was tried on separate indictments for separate episodes, as Illinois practice then required, and convicted of four of the ten murders. He was sentenced to death on January 28, 1986. Convictions and death sentences in some of the cases were reversed and retried on appeal, and the appellate history is long and not summarised reliably in any accessible source.
In January 2003 the governor of Illinois, George Ryan, commuted every death sentence in the state to imprisonment, which would have taken Johnson off death row; no source that can be checked records his sentence after that point, or his death. The remaining six killings were closed against him without a conviction, so the figure of ten is investigative rather than proved.