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Family member embrace following a shooting at Marjory Stoneman Douglas High School, Wednesday, Feb. 14, 2018, in Parkland, Fla.

People waiting for word from students at Coral Springs Drive and the Sawgrass Expressway just south of the campus following following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., Wednesday, Feb. 14, 2018.

Students are released from a lockdown 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)

A law enforcement officer rushes toward Marjory Stoneman Douglas High School following a shooting at the school in Parkland, Fla., on Wednesday, Feb. 14, 2018. (John McCall/South Florida Sun-Sentinel via AP)

Medical personnel tend to a victim following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Wednesday, Feb. 14, 2018.

Students wait to be picked up after a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., Wednesday, Feb. 14, 2018. A shooter opened fire at the Florida high school Wednesday, killing people, sending students running out into the streets and SWAT team members swarming in before authorities took the shooter into custody.

Students released from a lockdown are overcome with emotion following following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., Wednesday, Feb. 14, 2018.

Students released from a lockdown walk away following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Wednesday, Feb. 14, 2018.

A law enforcement officer directs traffic outside the school following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Wednesday, Feb. 14, 2018.

People gather waiting for word from students at Coral Springs Drive and the Sawgrass Expressway just south of the campus following following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., Wednesday, Feb. 14, 2018.

Students released from a lockdown embrace following following a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., Wednesday, Feb. 14, 2018.

Parents wait for news after a reports of a shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Wednesday, Feb. 14, 2018.

A student shows a law enforcement officer a photo or video from his phone, Wednesday, Feb. 14, 2018, in Parkland, Fla. A shooting at Marjory Stoneman Douglas High School sent students rushing into the streets as SWAT team members swarmed in and locked down the building. Police were warning that the shooter was still at large even as ambulances converged on the scene and emergency workers appeared to be treating those possibly wounded.

In this frame grab from video provided by WPLG-TV, students from the Marjory Stoneman Douglas High School in Parkland, Fla., evacuate the school following a shooting, Wednesday, Feb. 14, 2018.

Anxious family members wait for information on students, Wednesday, Feb. 14, 2018, in Parkland, Fla. A shooting at Marjory Stoneman Douglas High School sent students rushing into the streets as SWAT team members swarmed in and locked down the building. Police were warning that the shooter was still at large even as ambulances converged on the scene and emergency workers appeared to be treating those possibly wounded.

In this frame grab from video provided by WPLG-TV, emergency personnel wheel an injured person from the Marjory Stoneman Douglas High School in Parkland, Fla., following a shooting there on Wednesday, Feb. 14, 2018. (WPLG-TV via AP)

A law enforcement officer talks with students, Wednesday, Feb. 14, 2018, in Parkland, Fla. A shooting at Marjory Stoneman Douglas High School sent students rushing into the streets as SWAT team members swarmed in and locked down the building. Police were warning that the shooter was still at large even as ambulances converged on the scene and emergency workers appeared to be treating those possibly wounded.

In this frame grab from video provided by WPLG-TV, students from the Marjory Stoneman Douglas High School in Parkland, Fla., evacuate the school following a shooting, Wednesday, Feb. 14, 2018.

Anxious family members watch a rescue vehicle pass by, Wednesday, Feb. 14, 2018, in Parkland, Fla. A shooting at Marjory Stoneman Douglas High School school sent students rushing into the streets as SWAT team members swarmed in and locked down the building.

In this frame grab from video provided by WPLG-TV, students from the Marjory Stoneman Douglas High School in Parkland, Fla., evacuate the school following a shooting, Wednesday, Feb. 14, 2018. (WPLG-TV via AP)

Family members embrace after a student walked out from Marjory Stoneman Douglas High School, Wednesday, Feb. 14, 2018, in Parkland, Fla. The shooting at the South Florida high school sent students rushing into the streets as SWAT team members swarmed in and locked down the building. Police were warning that the shooter was still at large even as ambulances converged on the scene and emergency workers appeared to be treating those possibly wounded.