HUTCHINSON, Kan. (AP) — A 17-year-old Kansas boy has been found guilty of two counts of first-degree murder for setting a fire that killed his mother and sister.

Sam Vonachen also was convicted Wednesday of aggravated arson and attempted murder.

According to the Hutchinson News, during closing arguments, prosecutors said the teen wanted people to die. Vonachen was 14 at the time of the Sept. 26, 2013, blaze.

Vonachen’s attorney countered that he had a mental defect and wasn’t responsible for his actions.

Prosecutors say Vonachen waited until his three family members went to sleep before pouring gasoline around the stairs in his home and lighting it on fire. His father, Steven Vonachen, escaped. His mother, 47-year-old Karla Jo Vonachen, and his 11-year-old sister Audrey died in the blaze.