What the 911 calls in Georgia high school shooting reveal

The emergency dispatch center fielding reports of an active shooter at a Georgia high school was overwhelmed with 911 calls as the situation unfolded, according to local reports and recordings obtained by ABC News.

When shots rang out at Apalachee High School in Winder, Georgia, on the morning of Sept. 4, 911 calls from witnesses and parents began flooding the local emergency dispatch center, according to the recordings, released Friday by Barrow County officials and first reported by The Associated Press .

Reports from local outlets detail the difficulties callers faced when trying to reach a dispatcher.

Several 911 calls made in Barrow County around 10:20 a.m. were answered with an automated message that stated, "high call volume," FOX Atlanta affiliate WAGA reported. The Atlanta Journal-Constitution detailed that one caller was placed on hold for 10 minutes after calling 911.

Other 911 calls were from worried parents attempting to find out what was happening at the school.

One parent whose daughter goes to one of the nearby schools -- a middle and elementary school -- asked an operator whether there was a school shooter.

"We do have an active situation (at) Apalachee High School right now,” the operator responded. “We have a lot of calls coming in.”

Several 911 calls were not released under public record requests due to state laws that exempt recordings with the voice of someone younger than 18 years old from being released, according to the AP.

Four people were killed after the suspected gunman, 14-year-old Colt Gray, used an AR-15-style rifle to open fire inside the school, according to the Georgia Bureau of Investigation. Seven of the nine people who were injured suffered gunshot wounds, according to the GBI.

Colt Gray is charged with four counts of felony murder. His father, Colin Gray, is charged with four counts of involuntary manslaughter, two counts of second-degree murder and eight counts of cruelty to children for his alleged involvement by knowingly allowing his son to possess the weapon used in the shooting, the GBI said

Investigators believe Colt Gray received the AR-style gun used in the shooting as a Christmas present from his father, according to sources.

Both Colt Gray and Colin Gray made their first court appearances last week and will return on Dec. 4. Neither has entered a plea.

Apalachee High School students are scheduled to return to class on Sept. 23, the AP reported.

ABC News' Faith Abubey and Emily Shapiro contributed to this report.