Former student opens fire at Florida high school, killing at least 17

Medical personnel tend to a victim following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Wednesday, Feb. 14, 2018. (John McCall/South Florida Sun-Sentinel via AP)

PARKLAND, Fla. (AP) - A former student opened fire with a semi-automatic rifle at a Florida high school Wednesday, killing at least 17 people and sending hundreds of students fleeing into the streets in the nation's deadliest school shooting since a gunman attacked an elementary school in Newtown, Connecticut.

The shooter, who was equipped with a gas mask and smoke grenades, set off a fire alarm to draw students out of classrooms shortly before the day ended at one of the state's largest schools, officials said.

Authorities offered no immediate details on the 19-year-old suspect or any possible motive, except to say that he had been kicked out of Marjory Stoneman Douglas High School, which has about 3,000 students.

Students who knew the shooter, identified as Nikolas Cruz, described a volatile teenager whose strange behavior had caused others to end friendships with him, particularly after the fight that led to his expulsion.

Frantic