Transcript for School deputy failed to respond on time resigns
Next to the scrutiny and frantic moments when that gunman opened fire on students in parkland, Florida. The Broward county sheriff's office investigating reports that even police on the scene may have hesitated to take immediate action. This as officials are already looking into why an armed school deputy, Scott Peterson, is accused of failing to take on the shooter. He has now resigned. ABC's Kenneth Moton with more. Reporter: Tonight, growing pressure on the Broward county sheriff's office. Sheriff Scott Israel tells ABC news his department is now investigating reports that at least three deputies waited instead of rushing into Stoneman Douglas high school during the deadly mass shooting. The allegations reportedly made by officers from a nearby police department who were also on scene. This week the deputy assigned to guard the school, resource officer Scott Peterson, resigned after the sheriff says he failed to act. Devastated, sick to my stomach. There are no words. Reporter: The missed opportunities to try to stop the alleged shooter, nicholkolas Cruz, from gunning down 17 students and educators are stacking up. The thing is I lost my mother a couple days ago, so like I'm dealing with a bunch of things. Reporter: That 911 call appears to be the voice of Cruz three months before the shooting. In another call, the woman who had first taken the teen in after his mother died. He has a lot of weapons. He put the put gun in the head of his brother before so it's not the first time, and he did that to his mom. Reporter: Records show deputies responded to 18 calls related to Cruz before the shooting. ABC news also obtained the transcript of the tipster who called the FBI last month. The woman saying Cruz was, quote, going to explode, and she was worried about him getting into a school and just shooting the place up. The FBI admitting they failed to follow up on that tip. Tonight in parkland, anger is mounting at the deputy who has already stepped down. He was supposed to protect these kids and he didn't. Instead, my teachers, my friends threw their bodies on kids to protect them. Kenneth Moton joins us live now outside that high school. Some students may be returning there tomorrow? Reporter: Tom, students and parents were invited to a voluntary orientation tomorrow. Students will return to class on Wednesday. This difficult process of re-opening is happening as the final victim of this horrific mass shooting will be laid to rest tomorrow, Tom. A sad situation in Florida.
This transcript has been automatically generated and may not be 100% accurate.