(CNN)Annika Dean got text messages Wednesday that no parent ever wants to see.
"There's a school shooting drill," her son, Austin Dean, 14, wrote.
"It's really scary, they fired a gun," he continued, then: "IT'S NOT A DRILL."
The freshman at Marjory Stoneman Douglas High School was hiding with 30 others in a JROTC classroom as a gunman hunted down students and staff in a shooting that would leave 17 people dead in Parkland, Florida.
"He described that people had been running and screaming, and he told me he was on lockdown," Annika Dean told CNN affiliate WPTV. "He said, 'I love you, just in case.'"
In that moment, Dean knew, far too intimately, the horror unfolding for her son.
A year earlier, she'd survived the mass shooting at Fort Lauderdale-Hollywood International Airport that left five people dead and several wounded. Dean had cowered behind a luggage cart -- praying her two sons wouldn't have to grow up without a mother -- until a stranger shielded her from bullets, she told CNN last year, calling that man her "guardian angel."
As Dean hung Wednesday on every message ping from Austin, "there was nothing I could do," she told WPTV. "I was just grateful for every text he was sending me. It's different when it happens to your kid."
She also hoped Austin would remember what his mom had told him about surviving a mass shooting.
"I have talked to my kids, sometimes when we're walking through grocery stores," she said. "I've asked them: What would you do if this happened? Where would you go? Where would you hide?"
Austin made it home from Stoneman Douglas High. The daughter of Annika Dean's closest friend did not, she told CNN. Another friend's daughter was stable Friday after three surgeries, she said.
"They're just really on my mind right now," she said.
The thought that two people in her immediate family have survived mass shootings also weighs on Dean.
"It's incredibly rare," she said. "My brother said you're either one of the luckiest or the unluckiest, and I said it's both. It's both."
Update: This story has been updated with information from Annika Dean about the condition of Parkland students.