Story highlights The 5-year-old disappeared after Aramazd Andressian Sr. took his son to Disneyland

Police: Andressian's behavior after the disappearance was odd

(CNN) A California man pleaded guilty Tuesday to one count of first-degree murder in the death of his 5-year-old son, nearly a month after investigators found the boy's body.

The child disappeared shortly after his father, Aramazd Andressian Sr., took him on a trip to Disneyland in April.

Andressian, 35, of South Pasadena, California, was initially scheduled for a preliminary hearing on Tuesday, but instead changed his not guilty plea to guilty. He remained calm and serious during his court appearance.

Andressian's attorney, Ambrosio Rodriguez, said after the hearing that his client is "beyond words in regretting" his actions. Rodriguez said Andressian Sr. had given police information about where to find his son's remains.

Andressian faces 25 years to life in state prison. He will be formally sentenced on August 23.

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