Students and parents embraced after the shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Feb. 14.

PARKLAND, Fla. — In the first chaotic moments after a gunman opened fire at Marjory Stoneman Douglas High School in Parkland, Fla., 81 people called 911 desperate for help, including at least one boy who telephoned from inside the school and whispered urgently to an emergency dispatcher.

“Someone’s shooting up the school at Douglas,” he said, according to an audio recording of the call released on Thursday by the sheriff’s office in Broward County.

The office released recordings of 10 calls that sometimes depict panicked parents furiously texting their children at the school and relaying information to law enforcement. One father put his daughter on speaker phone and repeated what she said to the 911 operator.

“She doesn’t want to talk. She’s silent,” the father said. “She’s too afraid.”

“Tell her to be quiet,” the operator said. “Don’t make any noise. Everyone needs to be quiet in that room.”

The recordings, a fraction of the evidence that the authorities have been poring through since the Feb. 14 rampage, showed the uncertainty, fear and conflicting information in the minutes after officials believe the gunman opened fire. The suspect, Nikolas Cruz, 19, a former Stoneman Douglas High student, is accused of killing 17 students and school employees in about six minutes.

Separately on Thursday, Mr. Cruz, who was indicted this…