Sheriff Isreal said, "He was born in 1998 in September". His friend knew he liked guns a lot, but Santos said he never had any reason to think he might hurt other people.
A student describes rushing through Florida's Marjory Stoneman Douglas High School as police apprehended the gunman who killed 17.
Stoneman Douglas High School had an enrollment of about 3,100 students in the 2015-16 year, according to the National Center for Education Statistics.
Israel said that the suspect, Nikolaus Cruz, 19, was in custody but that a motive was unknown.
The gunman was identified by the sheriff's office as 19-year-old Nikolas Cruz.
She said she was "so f****** scared" and later claimed she had been evacuated. "We are working closely with law enforcement on the awful Florida school shooting", said another tweet from the President.
Feis has a long history with Marjory Stoneman Douglas High School, having graduated at this school back in 1999. "If anybody has any indicator that someone's going through a behavioral change, on social media if there are disturbing photos, perhaps bombs or firearms or just videos or pictures that are just not right, please make sure law enforcement knows about it".
Aerials above the Marjory Stoneman Douglas High School in Parkland show dozens of police vehicles.
Wednesday's massacre at a high school in Parkland, Florida marks the deadliest mass shooting in a high school in recent USA history, and tied for third deadliest at an educational facility.
"No child, teacher or anyone else should ever feel unsafe in an American school", he added.
Twelve people were killed inside the school and two died outside, Broward County Sheriff Scott Israel said.
One student fled the campus grounds and hid at a local retail store.
"Just a terrible day for us", said the superintendent of the county's school district, Robert Runcie.
"It's catastrophic", Israel said.
"I told her, 'Don't call me, because I don't want no one to hear your voice.' So, she's still trapped in a closet in there".
Law enforcement sources told CBS News that there are "numerous fatalities".