(PARKLAND, Fla.) -- A day after the Valentine’s Day massacre at a Florida high school left 17 people dead, the FBI said it received last year a threat of a potential shooter based on YouTube comments, including, "I'm going to be a professional school shooter," but couldn't track down the source.
"No other information was included with that comment which would indicate a time, location or the true identity of the person who made the comment," Robert Lasky, special agent in charge of the FBI Miami Division, said at a news conference Thursday.
The FBI conducted database reviews but was unable to “identify the person who made the comment," he added.
The agency has not confirmed a link to Wednesday's shooting at Marjory Stoneman Douglas High School in Parkland, Florida, but the post has the same name as the school shooting suspect: 19-year-old Nikolas Cruz.
Meanwhile, students, parents and faculty at the Marjory Stoneman Douglas High School in Parkland, Florida, are struggling to fathom why the former student allegedly opened fire there Wednesday as law enforcement officials searched for clues and the school district denied suggestions that it had been warned.
Besides the 17 killed, more than a dozen others were injured, some critically, after the suspect stormed the school.
Cruz -- who took an Uber to the school on Valentine's Day, according to Broward Schools Superintendent Robert Runcie -- slipped away from the campus by blending in with other students who were trying to escape, police said. He was later apprehended.
Cruz was a former student who had been expelled from Marjory Stoneman over disciplinary problems. He had been barred from carrying a backpack on campus before the expulsion, according to law enforcement sources.
The school had “received no warning, no hints, no tips” about the suspected shooter, Runcie, the superintendent, told ABC Miami affiliate WPLG-TV.
The suspect had an AR-15-style rifle that had apparently been legally purchased, according to a law enforcement official briefed on the investigation.
Since the shooting, "copycat" threats have been made at several schools in the wake of the deadly Valentine's Day attack, Broward Sheriff Scott Israel said at Thursday’s news conference.
"We will respond to every threat. Every threat we receive, we will not classify it as a copycat or prank call,” Israel said at a news conference. “We will respond in full and investigate it.”
But “any call that is made fictitiously, any fake call, any call that is made to take out resources at a time like this and place them in places where we don't need to be, we will do the full power of the sheriff's office. We'll investigate this and charge anyone accordingly with the maximum charge we possibly could for doing something so horrific, so pathetic.”
Among the 17 dead was school football coach and Marjory Stoneman Douglas High School graduate Aaron Feis, according to the sheriff.
A former high school classmate called Feis a "hero."
Teacher Scott Biegel died while saving others, according to student Kelsey Friend.
Biegel unlocked a classroom door and allowed students to enter, Friend told "Good Morning America.”
"I had thought he was behind me ... but he wasn't," Friend said, crying.
"When he opened the door, he had to re-lock it so we can stay safe. And he didn't get the chance to," Friend said, noting that her teacher was lying on the floor.
Among the parents left mourning is Fred Guttenberg.
His heart is broken after losing his daughter, Jamie Guttenberg, in the shooting, he wrote on Facebook.
"I am broken as I write this trying to figure out how my family gets through this," he wrote. "Hugs to all and hold your children tight."
President Donald Trump said from the White House Thrusday, "Our entire nation with one heavy heart is praying for the victims and their families. To every parent, teacher and child who is hurting so badly, we are here for you, whatever you need, whatever we can do to ease your pain. We are all joined together as one American family. And your suffering is our burden, also."
"No parent should ever have to fear for their sons and daughters when they kiss them goodbye in the morning," he said. "Each person who was stolen from us yesterday had a full life ahead of them. A life filled with wondrous beauty and unlimited potential and promise. Each one had dreams to pursue, love to give and talents to share with the world."
In a proclamation, Trump ordered all flags to fly at half-staff "as a mark of solemn respect for the victims of the terrible act."
Cruz was booked into the Broward County Jail and charged with 17 counts of pre-meditated murder. he has been answering investigators' questions, two law enforcement sources told ABC News. He will appear in court at 2 p.m. today.
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