— A threat posted on social media prompted a 90-minute lockdown at Heritage High School on Wednesday morning before authorities determined students were not in danger.

Wake Forest police spokesman Bill Crabtree said school officials contacted investigators about 8:30 a.m. after learning about the threat, which was posted on Twitter at 11:45 p.m. Tuesday. The user stated, "I'm shooting up Heritage."

Crabtree said officers traced the tweet to a 14-year-old boy in Pinellas County, Fla. They talked to the boy's mother and determined there was no threat to the school.

Police said they do not know whether the boy has any affiliation with Heritage High School, but he sent the tweet directly to the Wake County Public School System.

"At this time, since the tweet originated from Pinellas County, Florida, the authorities in Pinellas County will be assuming responsibility for the investigation," Crabtree said.

A spokeswoman with the Pinellas County Sheriff's Office said no charges were filed.

The school, at 1150 Forestville Road, was locked down at about 9:30 a.m. Heritage Elementary School and Heritage Middle School, which are nearby, were also locked down as a precaution, and officials asked parents not to pick up their children.

Wake County school officials initially classified the lockdown as "code red," which means there is a direct threat to the school or in the immediate area of the school. In a code red lockdown, buildings are secured and no one is allowed to enter or exit.

"We had to turn off the lights, and everyone had to get in the corner," Heritage High student Ryan Wetzel said.

Senior Nick Fisher said most people remained calm.

"I mean, a couple of people were kind of freaking out, but there's no reason to," he said.

The lockdown was lifted about 11 a.m.

"These steps are taken as a precautionary measure to ensure the safety of our students and faculty," Lisa Luten, a spokeswoman for the Wake County Public School System, said in a news release. "Once the police gave the school the all clear, the lockdown ended without any incident."

Luten said an employee who reviews all social media messages posted overnight found the tweet about 8:15 a.m. The user deleted the tweet shortly after the lockdown began.

Crabtree said Wake Forest police worked with the Wake County Sheriff's Office and the North Carolina State Highway Patrol to bring a quick resolution to the case.

"We greatly appreciate the relationship we have with law enforcement and WCPSS Security in responding to such situations," Luten said. "They work closely with us to ensure the safety of our students every day."

Luten also said she did not know whether the teen is connected to the school. But Fisher said the boy attended Heritage Middle School last year.