A Tenants Harbor man accused of killing a man with a shotgun says it was over a drug dispute. This according to court documents filed by police in Knox County Superior Court.40-year-old Andrew Kierstead made his initial court appearance in Rockland Monday.Police say he shot and killed 48-year-old Richard Mills at his Cushing home Thursday.Kirstead told police he owed Mills $250 for drugs and Mills wouldn’t give him anymore until he paid off the debt.Police say Kierstead lured Mills outside, telling him he needed his help to get his vehicle started. According to court documents, while Mills was looking under the hood Kierstead got a 12-gauge shotgun from inside the truck.Kierstead told State Police Detectives that Mills told him to put the gun away before someone got hurt. Police say Kierstead shot mills four times. An autopsy done on Mills in Augusta revealed he had been shot four times in the front of his body with 12 gauge slugs and once in the right buttocks with birdshot.According to court documents, Kirstead told police he tried to overdose on drugs he found in Mills’ house after the shooting. He later woke up and thought he dreamt the whole thing. He went outside and saw Mills’ body on the ground and called 911. Kierstead told police he was hooked on Perocet, Vicodin, Methadone and other pills. According to police, Kierstead said he had been buying drugs from Mills for the past 10-15 years and he blamed Mills for ruining his life.Kierstad’s attorney, Steve Peterson, told reporters outside the courthouse he hasn’t ruled out a defense based on Kierstead’s mental state. “I think his state of mind on the date this happened both before and after the incident will be critical to this case. I don’t know if that answers your question, but the state of mind in a murder charge is knowing or intentional conduct, so clearly that’s going to be an issue.”Kierstead is scheduled to be back in court later this month.He’s being held without bail at Knox County Jail.