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TOPSHOT - Marjory Stoneman Douglas High School staff, teachers and students return to school greeted by police and well wishers in Parkland, Florida on February 28, 2018. 
Students grieving for slain classmates prepared for an emotional return Wednesday to their Florida high school, where a mass shooting shocked the nation and led teen survivors to spur a growing movement to tighten America's gun laws. The community of Parkland, Florida, where residents were plunged into tragedy two weeks ago, steeled itself for the resumption of classes at Marjory Stoneman Douglas High School, where nearby flower-draped memorials and 17 white crosses pay tribute to the 14 students and three staff members who were murdered by a former student.
 / AFP PHOTO / RHONA WISE        (Photo credit should read RHONA WISE/AFP/Getty Images)
RHONA WISE/AFP/AFP/Getty Images
TOPSHOT - Marjory Stoneman Douglas High School staff, teachers and students return to school greeted by police and well wishers in Parkland, Florida on February 28, 2018. Students grieving for slain classmates prepared for an emotional return Wednesday to their Florida high school, where a mass shooting shocked the nation and led teen survivors to spur a growing movement to tighten America's gun laws. The community of Parkland, Florida, where residents were plunged into tragedy two weeks ago, steeled itself for the resumption of classes at Marjory Stoneman Douglas High School, where nearby flower-draped memorials and 17 white crosses pay tribute to the 14 students and three staff members who were murdered by a former student. / AFP PHOTO / RHONA WISE (Photo credit should read RHONA WISE/AFP/Getty Images)
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This image made available by the Broward County Sheriff's Office on Sunday, Feb. 18, 2018, shows Sheriff Scott Israel, holding the hand of Anthony Borges, 15, a student at Marjory Stoneman Douglas High School. The teenager was shot five times during the massacre on Valentine's Day that killed 17 students. Borges is being credited with saving the lives of at least 20 other students. (Broward County Sheriff's Office via AP)
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This image made available by the Broward County Sheriff's Office on Sunday, Feb. 18, 2018, shows Sheriff Scott Israel, holding the hand of Anthony Borges, 15, a student at Marjory Stoneman Douglas High School. The teenager was shot five times during the massacre on Valentine's Day that killed 17 students. Borges is being credited with saving the lives of at least 20 other students. (Broward County Sheriff's Office via AP)
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(CNN) —  

The FBI failed to act on a tip about Nikolas Cruz, the confessed shooter in the Parkland, Florida, school massacre, the bureau said in a statement on Friday.

A person close to Cruz contacted the FBI on January 5 to report concerns about him, the FBI said in a statement Friday. But the bureau did not appropriately follow established protocols in following up on the tip.

“The information was not provided to the Miami Field Office, and no further investigation was conducted at that time,” the statement said.

The stunning admission – which prompted Florida Gov. Rick Scott to call on FBI Director Christopher Wray to resign – is sure to raise further questions about whether the FBI could have prevented the shooting at Marjory Stoneman Douglas High School, which left 17 dead.

The FBI said the caller provided information about “Cruz’s gun ownership, desire to kill people, erratic behavior, and disturbing social media posts, as well as the potential of him conducting a school shooting.” The information should have been assessed as a “potential threat to life,” the bureau said.

Wray said the bureau is still investigating what happened.

“We have spoken with victims and families, and deeply regret the additional pain this causes all those affected by this horrific tragedy,” Wray said in the statement. “All of the men and women of the FBI are dedicated to keeping the American people safe, and are relentlessly committed to improving all that we do and how we do it.”

Attorney General Jeff Sessions ordered a review Friday into how the Justice Department and FBI respond to indications of potential violence. The Justice Department will review not just how the Cruz tip was missed but how authorities respond to similar situations, Sessions said.

“We will make this a top priority,” Sessions said in a statement. “It has never been more important to encourage every person in every community to spot the warning signs and alert law enforcement. Do not assume someone else will step up – all of us must be vigilant. Our children’s lives depend on it.”

Sen. Marco Rubio, R-Florida, also called for the House and Senate to conduct investigations into how the FBI reviews public tips in similar instances.

Disturbing signs

Cruz has confessed to police to being the gunman, according to a probable cause affidavit. His public defender described him as a “deeply disturbed, emotionally broken” young man who is coming to grips with the pain he has caused.

But as details about Cruz have emerged, so have indications that signs were missed in the months leading up to Wednesday’s rampage.

On Thursday, it was revealed that the FBI also was warned in September about a possible school shooting threat from a YouTube user with the same name as Cruz, according to a video blogger.

Ben Bennight, the 36-year-old YouTube video blogger from Mississippi, noticed in September an alarming comment on a video he’d posted. He told CNN he immediately contacted the FBI.

“Im going to be a professional school shooter,” read the comment, left by a user with the name Nikolas Cruz.

And documents obtained by CNN show that law enforcement officers responded to Cruz’s house on 39 occasions over a seven-year period. No police reports were immediately available for those calls so it was not possible to determine whether Cruz was involved.

Meanwhile, Cruz’s digital footprint offers other disturbing glimpses into his mind.

He hurled slurs at blacks and Muslims, and according to the Anti-Defamation League, had ties to white supremacists. He said he would shoot people with his AR-15 and singled out police and anti-fascist protesters as deserving of his vengeance.