Under the Twitter handle @TheCaptainAidan, the freshman tweeted photos of classmates crouched under tables in a classroom. One student could be seen checking a mobile phone.
The tweet was captioned: My school is being shot up and I am locked inside. I’m ing scared right now.
Students also posted to Snapchat to share updates. In one snap, blood can be seen on the classroom floor.
Israel described the mass shooting at Marjorie Stoneman Douglas High School in Parkland as catastrophic.
The shooting suspect, Nikolas Cruz, was taken into custody less than a mile from the scene. The 19-year-old former Douglas student was expelled for disciplinary reasons, according to Israel.