John Ingvar Lövgren was born in Norrköping on October 22, 1930. Both his parents died while he was very young and he was raised in foster homes. As an adult he drank heavily and was convicted several times for indecent exposure, and he was in and out of mental hospitals between 1953 and 1961. He worked as a gardener. From 1961 he lived with his grandmother at an old people's home in Gröndal.
He killed four people in Stockholm between 1958 and 1963. Agneta Nyholm, twenty-six, was killed in the basement of the block of flats where she lived in Fruängen on the night of June 27, 1958. Greta Löfgren, sixty-two, was killed in her own home. The last two were children: Berit Glesing, six, and Ann-Kristin Svensson, four. It is those two that the Swedish press meant by the name it gave him, Flickmördaren, the girl killer.
The investigation after the 1963 killing was what finished it. Witnesses identified him, among them the dead girl's playmates. While getting away he threw out her clothes, and that led the police back into his own neighbourhood.
He confessed to four murders and was convicted of three: Greta Löfgren, Berit Glesing and Ann-Kristin Svensson. He was assessed as dangerous to others and sentenced to closed forensic psychiatric care at Salberga rather than to prison.
The fourth was never charged. He confessed to the murder of Agneta Nyholm and Swedish accounts say there was other evidence besides the confession, but no prosecution was ever brought. The case reached the statute of limitations in 1973 and remains officially unsolved, while the police treated it as cleared on the strength of what he told them.
He was later known as John Ingvar Andersson. He was discharged from care because of his very poor health, and died of cancer on February 9, 2002, aged seventy-one. He was buried at the new cemetery in Sala.
The Sjöwall and Wahlöö novel The Man on the Balcony, published in 1967, was based on this case.