Mass shooting suspect Nikolas Cruz said a demon in his head told him to burn, kill and destroy “anything” before he allegedly killed 17 people at a Florida high school, transcripts of a police interview revealed Monday.

Cruz, 19, described to Broward County Sheriff’s Detective John Curcio a male voice inside his head that he called “the evil side.”

Curcio asked Cruz what this voice told him.

“Burn. Kill. Destroy,” Cruz responded.

“Burn, kill, destroy what?” Curcio asked.

“Anything,” Cruz responded.

The suspect said he was in constant battle with “the voice.”

“The voice is in here,” Cruz said, pointing to his head. “And then it’s me. It’s just regular me trying to be a good person.”

Cruz said the voice urged him to shoot people at a park a week or two before the Feb. 14 assault on Marjory Stoneman Douglas High School in Parkland.

Asked why he didn’t go on a killing spree then, Cruz said: “I … I don’t know.”

The Associated Press and other Florida news media outlets had pressed for transcripts of the interrogation to be made public, before prosecutors released a heavily redacted 216 pages.

Cruz’s answers about the shooting itself were blacked out.

But he did talk at length about his difficult family life — which included the death of his father 15 years ago and the passing of his mom, from pneumonia, in November.

At points in the interrogation, Curcio left the room, but Cruz’s words were still recorded.

Cruz cursed at himself and said he wanted to die.

“You’re nothin’,” Cruz told himself.

The detective allowed Cruz’s brother into the interview room and the suspect appeared to awkwardly laugh when he was called a “monster.”

“You — your — people think you’re a monster now,” 18-year-old brother Zachary Cruz told him.

“A monster?” the confessed killer said.

“You’re not acting like yourself. Like, why? Like, we’ve … this is not who you are. Like, come on. Why did you do this? This is … don’t even laugh at me,” Zachary Cruz said.

“I’m sorry, dude,” said Nikolas Cruz.