One injured victim was seen being placed into an ambulance on a stretcher. Another two incidents were gun suicides, claiming the lives of one student and one adult on school property.
Talk show host Ellen DeGeneres said: "No words, no actions, no laws are enough until we end this epidemic of school shootings in our country".
Yet even as officials gain a clearer understanding of how the shooter conducted the attack, law enforcement is opening its investigation into a still more hard question: why.
Administrators sent an email to teachers warning them about Cruz, Gard told the paper.
"The alarm went off so we had to evacuate from our classes", she said.
Earlier in the day, there was a real fire drill and many students and teachers thought it was a false alarm when they heard the siren again.
Some of the terrified students hid inside the closets and under desks.
"We were in there for probably 40 minutes". We had to squeeze through a fence to get out.
My prayers and condolences to the families of the victims of the awful Florida shooting.
She says it's' a healing process."It happened today, but what about tomorrow, what about the next day or the next year will i ever be ok with going back to school and its sad that kids have to feel that way", she said.
Paramedics were treating those who appeared to be students with injuries.