HUTCHINSON, Kan. (AP) — Testimony is underway in the southern Kansas trial of teenager charged as an adult in the killing of his mother and 11-year-old sister in a 2013 house fire.

Samuel Vonachen is being tried in Reno County on two counts of premeditated first-degree murder.

Vonachen was 14 in September 2013 when he allegedly used gasoline to ignite his family’s Hutchinson home. The blaze killed 11-year-old Audrey Vonachen and their mother, 47-year-old Karla Jo Vonachen. His father escaped.

A prosecutor told jurors Tuesday during opening statements that Vonachen was a compassionless psychopath who wanted his family to die. A defense attorney countered that his client has a dissociative disorder and didn’t know what he was doing.