Deputies with the Norwalk sheriff's station responded to the school on Friday to investigate a criminal threats call. The deputies learned a school security officer overheard a "disgruntled student" threaten a school shooting.
The investigation resulted in finding a collection of weapons and ballistic evidence at the student's home, authorities said.
Authorities did not provide further details Tuesday, but said they will be holding a press conference Wednesday morning.
The threat came only two days after a former student opened fire and killed 17 students and faculty at a Florida high school.