(CNN) When a shooting erupted at Marjory Stoneman Douglas High School in Parkland, Florida, the first thing some students did was contact their parents.

Those parents' voices could be heard on the line in 911 calls released by the Broward County Sheriff's Office on Thursday.

One woman's voice cracked as she read the dispatcher a text message from her son: "Shot, shot, shot. Mom. God." Another woman told her daughter to play dead.

At least one person called from inside the school. "Marjory Stoneman Douglas High School is being shot up," the caller whispered.

The Broward County Sheriff's Office released a sampling of the calls operated received on February 14. Here are some excerpts:

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