Tipster warned FBI school shooting suspect could 'explode'

— -- The female tipster close to accused Florida high school shooter Nikolas Cruz told the FBI Cruz was "going to explode," according to a transcript of the Jan. 5 call more than a month before the shooting obtained by ABC News.

"It’s so much and I know he’s – he’s going to explode," the woman said.

The five-page transcript of the call obtained by ABC News detailed what had been reported the FBI knew about Cruz before he killed 17 students and teachers at his former school in February. The FBI has admitted to failing to follow up on the tip called in to the FBI's call center in January and sharing it with the bureau's FBI field office.

The tipster also provided details about Cruz’s concerning social media activity, identifying four Instagram accounts and troubling posts, and sharing details about his upbringing, foster family and concerning behavior.

“I just want someone to know about this so they can look into it,” the tipster said. “If they think it’s something worth going into, fine. If not, um, I just know I have a clear conscience if he takes off and, and just starts shooting places up.”

On the call, an intake specialist located in West Virginia, asked the caller for information about Cruz, and whether he had made any threats of violence or “talk about ISIS.”

The tipster, whose name is redacted from the transcript but identified as an "unknown female," said Cruz “expresses different things” on social media “and then he takes it off.”

“Just recently, now he has switched it to he wants to kill people. And then he put that on his Instagram and about two days later, he took it off,” the tipster said.

She also said she had previously called the Parkland Police Department with warnings about Cruz, giving an officer with the local department "all the information I had."

The tipster described Cruz as a violent child who killed animals, posted frequently about firearms and ISIS, and was “thrown out of all these schools because he would pick up a chair and just throw it at somebody, a teacher or a student because he didn’t like the way they were talking to him.”

“It’s alarming to see these pictures and to know what he’s capable of doing and-and what could happen,” the tipster told the FBI on the call, according to a transcript reviewed by ABC News. ”I just think about, you know, getting into a school and just shooting the place up.”

“I didn’t know whether to call you or Homeland Security or who, but like I said … when you look into this you can make the decision as to whether you want to go further or not,” the tipster told the FBI in the call.

“I just want to, you know, get it off my chest in case something does happen and I do believe something’s going to happen,” the tipster said.

The intake specialist did not say if the agency would be following up with the caller.

The FBI has admitted to not following proper protocol after the shooting at the high school last week that left 17 people dead, and properly following up on the Jan. 5 call to the tip line.

“We have determined that these protocols were not followed for the information received by the PAL on January 5. The information was not provided to the Miami field office, and no further investigation was conducted at that time,” the FBI said in a statement last week.

FBI Director Christopher Wray has come under fire for the episode, including from Florida Gov. Rick Scott, who has called for Wray to resign over the FBI’s “failure to take action.”

ABC News' Jack Date and Mike Levine contributed to this story.