A 17-year-old junior at Ponchatoula High School was arrested Thursday and is accused of using social media to send a bomb threat at the school, the Tangipahoa Parish sheriff said.

In an online post made about 8:30 p.m. Wednesday, Calvin Richardson, who lives in Ponchatoula, instructed those who read the post to “Be ready,” adding that the threat was real and students should not go to school.

Richardson was taken into custody about 9:45 a.m. Thursday while sitting at his desk at school. He was in the process of posting a second threat, according to a Sheriff’s Office news release.

Sheriff Daniel Edwards noted this was the second such threat at the school in the past week. While there has been an arrest in this case, no arrests have been made in the threat from a week ago when a caller from Carrollton, Texas, warned of an explosive device at the school. That investigation remains active.

Edwards and others at a Thursday afternoon news conference said the consequences are severe, and students should not take the making of such threats lightly. Edwards said Richardson has already confessed to making the social media posts.

Detective Toby Aguillard said the student was cooperative and remorseful but also shocked that he was caught.

Edwards said Richardson had not had any problems before today.

Richardson was booked on two counts of terrorizing and two counts of false planning of a planned bombing on school property.