According to authorities, when Nikolas Cruz entered Marjory Stoneman Douglas High School in Parkland, Florida on February 14, 2018, he opened fire with an AR-15 assault rifle, shooting innocent students and faculty, killing 17 and injuring many others. One of those killed was 17-year-old Joaquin Oliver.

TELL DR. PHIL YOUR STORY: Are you involved in a story that has made the headlines?

Jack, a teen who also attends the high school, reads a letter he wrote to his good friend who lost his life. And, a Spanish teacher at the high school grows emotional as she reflects on her former student.

WATCH: ‘There’s No Words To Describe The Feeling Never Seeing Your Friends Again,’ Says Survivor Of Florida High School Mass Shooting

On Thursday’s episode of Dr. Phil, hear from other students who survived the massacre and what they say it was like being locked in classrooms hiding from the alleged killer. Check here to see where you can watch.

TELL DR. PHIL YOUR STORY: I'm Living A Nightmare!

Survivors Of Columbine High School Shooting Share How Their Lives Have Been Affected During The Last 19 Years