He claims to have committed the murder to satisfy his curiosity about how it would feel to kill someone.

“I was wondering what murder would feel like because Bundy and the Zodiac they all say murder is the best human in the world so I'm like I'm going to try that”

He expresses that he was initially deceived by his son and found it hard to believe Brian was capable of such violence.

“and he was so sincere I I I I took it all I want to believe him because he's my son”

She believes that Brian's behavior was influenced by his fascination with morbid subjects and crime scene investigation.

“he's had a little bit of a fascination with The Morbid but he was channeling it I thought into becoming a crime scene investigator”