TAMPA — A custodial employee working for a contractor at the Academy of the Holy Names was arrested Tuesday, one day after she threatened to "shoot up" the school, authorities said.

Aniya L. Smalls, 23, made the threat while she was being escorted out of the private school at 3319 Bayshore Blvd. about 3:30 p.m. Monday, according to a Tampa police report. Smalls had just been terminated by the company hired by the school to clean the building, Suncoast Construction and Maintenance, police and school officials said.

As she was walked out the front door, Smalls said, "I'm coming back and I'm going to shoot this place and all you people up," an arrest report says. Several witnesses including students in the lobby area heard the threat, and "students were in fear that she will return and harm them," the report says.

At that point, a school staff member called police, said Emily Wise, the school's director of marketing and communications.

"We were hoping they'd apprehend her that night," Wise said.

When Smalls hadn't been arrested by 8 p.m., the school took police's recommendation to operate on modified lockdown Tuesday, meaning students could move freely in the building but could not go outside, Wise said.

School president Art Raimo sent a letter to parents notifying them of the lockdown plans.

Smalls was arrested at her Tampa apartment on Tuesday afternoon and charged with falsely threatening to use a firearm to commit violence, a second degree felony, records show. Tampa police spokesman Steve Hegarty said investigators concluded that the threat was not credible.

The incident has prompted the school to tighten background checks for contracted cleaning employees after school officials learned Smalls was already wanted for violating probation for an unrelated misdemeanor arrest.

In a second letter to parents sent Tuesday, Raimo said school officials were told that Smalls passed a Level 2 background check because she had no felony convictions on her record. Raimo wrote that all contracted custodial employees will be subject to the more rigorous screening that faculty and staff must pass.

Wise, said the school has used Suncoast Construction and Maintenance for 20 years without a problem.

Contact Tony Marrero at tmarrero@tampabay.com or (813) 226-3374.