A 12-year-old has been arrested in connection with a text threatening a mass shooting at Coakley Middle School sent Friday, Norwood Police announced Sunday afternoon.

On Friday morning, the department said, police received a screenshot of a group text in which a sender was warning of a shooting to take place at the middle school. The screenshot cropped the message, but police later learned the texter detailed the event was planned for Monday.

The identity of the arrested student was not released on Sunday. Police said previously over the weekend they did not find the threat credible but would keep police staffed at the school Monday.

The number the threat was sent from was unknown, police said, while all the others belonged to students at the school.

The text refenced an “army” and a motive stemming from an unspecified event 17 years ago and warned the phone number couldn’t be traced, Norwood PD said.

Details in the message led detectives to believe the sender was another student, the department said. Police reported they questioned the students on the message and sent uniformed and plainclothes officers to the school for extra security.

Though efforts were made to mask the origin of the phone number, police said, investigators identified and briefly spoke on the phone to the student who sent the threat by 10:30 a.m. Friday. The 12-year-old was reportedly traveling out of state with their family at the time.

Norwood Public Schools families were updated twice Friday morning, and by the afternoon, were told the police “considered the threat not to be credible.” On Saturday, Norwood Police Chief William Brooks said, the department would “release more information prior to the start of school” and keep officers at the school Monday.

“The purpose is not threat-based, but to assure students that they are safe,” Brooks said in the Saturday update.

A second threat directed at the local high school circulated Friday, spoofed to appear as though it came from the same number. Police reported they verified with the provider the second threat was not from the same number and stated they “give no credence to that remark.”

On Sunday, the student and family were back, the report said. Detectives executed a search warrant, seized the student’s phone and arrested the teen.

“The student has confessed in the presence of the family,” Norwood Police said in a Facebook update Sunday. “There were no firearms in the student’s home. The student will not be in school Monday.”

The department stated they are “pleased that we have been able to bring this investigation to a successful conclusion,” in the report Sunday.