ST. JOSEPH, Mo. (AP) — A man already in prison for killing his son pleaded guilty to killing his cellmate in Buchanan County jail.

Tony King, of Bethany, was sentenced to another 20 years in prison after pleading guilty Thursday to second-degree murder in the June strangling death of 25-year-old Michael Bozarth, his cellmate in the Buchanan County Jail.

At the time of Bozarth’s death, King was serving life in prison for killing his 7-year-old son, then setting their Harrison County home on fire. The 20-year sentence will be served consecutively to his sentence for killing his son.

Defense attorney Shayla Lewis claimed King suffered from mental illness and hadn’t received any treatment before he killed Bozarth.