TALLAHASSEE, Fla. -- New audio recordings and an updated timeline from the Florida school shooting give a clearer picture of how the Valentine's Day attack unfolded. Fourteen students and three adults were killed in the massacre, and 16 others were wounded.

The first cries of help from inside had to be whispered.

"911, what is your emergency?" a dispatcher asked.

"Someone is shooting up Marjory Stoneman Douglas," a caller told the dispatcher.

"Someone is doing what?" the dispatcher asked. "Hello? Hello?"

The caller was afraid of making too much noise.

"Marjory Stoneman Douglas High School is being shot up," the caller whispered.

"It's being shot up?" the dispatcher asked. "Are you at the school? I can't hear you. Are you at the school?"

The caller hung up.

As students tried to stay quiet inside, first responders struggled to get specifics about what was happening. One dispatcher relayed information from a mother who was on the phone with her daughter inside the school.

"Ok, where is her daughter hiding at? Like what room is she in?" a first responder asked.

"Twelve-hundred building," the dispatcher responded.

"I understand she's in the 1200 building. Does she know what room she's in?" the woman asked. "Where she's hiding at?"

"Does she have a class -- " the dispatcher asked. "She doesn't want to talk. The girl is silent. She's too afraid."

According to a new timeline of events released late Thursday from the Broward County Sheriff's Office, the first call came in less than a minute after the first shots were fired. Eighty-one calls were made in 73 minutes. Ten of those calls were released Thursday. All but one came from outside the building.

One call came from a panicked mother who could be overheard speaking directly to her child.

"I love you. It's going to be fine," the mother said. "Can you hide somewhere? Can you play dead? If he shoots, you need to play dead. If he shoots, play dead."