What sounded like gunfire outside Powell High School Tuesday morning and prompted a hard lockdown by staff and students turned out to be an "electrical disruption" that occurred during maintenance to an air conditioner, according to a statement released by the high school.

Principal Chad Smith tweeted out the statement Tuesday afternoon clarifying that "at approximately 10:26 a.m. while an air conditioner was being serviced at Powell High School, an electrical disruption occurred thus interrupting power to several parts of the school."

What followed was "several large cracking sounds" that were heard by school security, the statement noted.

"Based on their training and their directive we went into a hard lockdown to ensure the safety and security of our students and staff," the statement read.

Nearly 1,300 students at Powell High School took cover in locked classrooms, anxiously awaiting news about whether those loud pops heard by staff signaled a school shooter was on the loose.

“It was calm, but you could tell people were scared," junior Peyton Hubbs told the Knoxville News Sentinel. "Some people were getting upset and wanting to contact their families (during the lockdown).”

In the end, authorities found no threat and ended the lockdown, providing relief for students, staff and anxious parents.

“There was panic until I heard from my kids," said Ann Quillen, who has two children at Powell. "They texted me back after I texted them and said they were fine, and I trusted they were in good hands.”

Quillen said the school did a good job keeping parents informed about the situation, sending two emails about what was happening.

Knox County Sheriff's Office spokeswoman Kimberly Glenn said Tuesday afternoon that authorities had not confirmed any shots were fired and investigators considered whether something else produced the sound. Deputies planned a second sweep of the school with police dogs after students and staff left for the day.

Officers first swept the school after it was placed on hard lockdown around 10:30 a.m., Glenn said. A school resource officer had called police to report hearing shots fired outside near the school, located at 2136 West Emory Road. Staff members said they heard four to six "pops."

Classes continued Tuesday at Powell after the incident, but parents were able to pick up their child early if they wanted to, said Carly Harrington, Knox County Schools spokeswoman.

"Your children are safe," Glenn said.

Dozens of police cars sped from downtown to the area after the call came in, and officers began securing surrounding buildings and cars and searching campus.

The high school's statement emphasized that at not time were any students "in immediate danger" and the concentration of armed police was done "out of an abundance of caution."

The lockdown was lifted shortly before noon.

Hubbs left school around 12:30 p.m. Hubbs said his class gathered in the corner of the room with the lights off after the lockdown was announced.

"They’ve especially, Powell, they’ve taught us pretty good and prepared us pretty good for what we need to do," Hubbs said. "The teacher I had in my class made me feel safe.”

Hubbs said he decided to leave after the lockdown was lifted because it was a scary situation.

Larry Holloway, who has two students at Powell, said he came straight to the school after hearing about the incident.

“It’s scary," Holloway said. "To send your kids to school, you think you don’t have to worry about this.”

Holloway said he got to the school around 11 a.m.

"I’m relieved, and now I’m debating whether or not I trust sending them back," Holloway said. "Homeschooling is starting to sound like a pretty good option.”

During the lockdown, a helicopter hovered above the school and officers with rifles patrolled the area. Side roads near the school were closed.

Bailey Trumm, a senior at Powell, told the News Sentinel the school's principal, Chad Smith, announced the lockdown on the intercom around 10:30 a.m. About 20 minutes later, an assistant principal went classroom to classroom to tell students to stay away from doors and windows and stay near the walls.

Students were "anxious and concerned," Trumm said.

Bailor Hughes, a senior, told the News Sentinel students were sitting on the floor "being silent and it's been nervous and anxious."

Glenn said authorities "have this situation under control."

Powell Middle School and Powell Elementary were also locked down during the incident.

News Sentinel reporters Erica Breunlin, Aaron Torres and Ryan Wilusz contributed to this report.