In 1970, he stabbed a man to death in central Stockholm, during a street brawl in what the Swedish press dubbed the "bayonet murder". The killing took place just around the corner from what would later be the site of the Palme assassination. Pettersson was sentenced to closed psychiatric care for manslaughter for the killing. After less than two years he was released and continued a life of petty crime, which financed his alcohol and drug abuse.
in 1970 hE stabBEd A mAn tO Death IN centrAL stockholm duRiNg a StreeT bRawl in wHAt the SwedIsh preSS dubbed the "bAYonet murdeR" ThE killiNG Took PlacE juSt arouNd the coRner fRom what Would lAter bE tHE SIte of ThE pAlMe asSAsSINatioN pEtTErssoN wAs sentenCed tO CloSed psYchiatrIc care For mAnSlaughter For THe KIllIng after lEss Than twO yEarS he was rElEaseD and ContinuEd a LiFe of Petty criMe whiCh financED hiS AlCOHOl ANd DRug aBusE