LANSING, Mich. -- A Michigan man who told police he killed his 5-year-old stepdaughter and set fire to the family's apartment after she interrupted his nap has been convicted of first-degree murder.

Ingham County Circuit Court Judge Joyce Draganuchuk also found 25-year-old Thomas McCIellan of Holt guilty of first-degree child abuse and first-degree arson on Friday. He's scheduled to be sentenced Aug. 23 to life in prison without parole.

Defense lawyer Patrick Crowley argued that a second-degree conviction would be more appropriate.

Authorities say McCIellan told officers he stabbed Luna Younger on Nov. 1 and then set fire to the Lansing-area apartment to destroy evidence of the killing. During a taped confession played during the trial, McCIellan said he killed the girl because she interrupted his nap and asked for something to eat.

"I told her it wasn't dinner time," McClellan told investigators in the, reports the Lansing State Journal.

He reportedly said he tried to get the girl to leave his room, but she sat on the floor.

"It tipped me over the edge," McClellan told investigators, the paper reports. "She gave me more attitude."

That's when he said he fatally stabbed the girl. Prosecutors said he then wrapped the child's body in blankets and set it aflame in an attempt to cover up the crime, according to the Lansing Journal.

Arguments and testimony in his three-day trial reportedly wrapped up Thursday. McClellan did not take the stand in his own defense, reports CBS affiliate WLNS.

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