ROCHESTER, N.Y. — A Rochester student accused of threatening online to shoot up a high school that she didn’t attend has been arrested.

Abigail Hernandez pleaded not guilty Wednesday to making a terroristic threat, online court records show. Her lawyers’ office was closed and not accepting phone messages Saturday, and no telephone number could immediately be found for her home.

Hernandez, 21, is in federal immigration custody, according to city officials. Deputy Mayor Cedric Alexander says Hernandez had obtained Deferred Action for Childhood Arrivals status. It allows some people brought to the U.S. illegally as children to stay.

A Feb. 15 comment on East High School’s Facebook page vowed the commenter would come the next morning and “shoot all ya,” ending with a vulgarity, authorities said.

“The threat referenced the shooting and sympathy of the school shooter in Parkland, Florida,” Alexander said. The Feb. 14 attack in Parkland killed 17 people.

Although the comment wasn’t in Hernandez’s name, investigators traced it to her, authorities said. Police found a shotgun in Hernandez’s home when they arrested her Tuesday, Alexander said.

It’s unclear what school Hernandez has been attending. East High School Superintendent Shaun Nelms said she wasn’t currently a student at his school but did attend another in the city. Rochester Police Deputy Chief La’Ron Singletary said he was unsure why East High was the target of the threat.

Nelms said in a letter to parents that he couldn’t comment on the investigation but thanked police for their work.