HIGHLAND PARK (CBS 11 NEWS) – After several threatening notes and a dozens of bullets were found inside Highland Park High School, the person or group behind the threats remains a mystery.

University Park police officers and FBI agents patroled the school once again Friday, but this time they had metal detecting wands at their disposal.  Not all students were checked.

“We used them as we feel is appropriate and necessary,” said Walter Kelly, principal at Highland Park High School.

Police have questioned dozens of students but not named any suspects.

The DNA analysis of the notes and the bullets is not yet complete. The FBI is conducting the forensic testing.

Friday morning, some parents were unsure about bringing their kids to school.

“We’re just tired as parents. You don’t want to drop them off and worry. I mean, we wait by our phones now because we are so worried they are going to call us and say,’Mom, we’re locked in a closet again,'” said Jennifer Patterson, whose daughter attends Highland Park High School.

Some parents were upset that the school had not scheduled an informational meeting. so they called one of their own.

“The parents of very, very frustrated with that. The parents haven’t been told what they need,” said Pamela Kripke. who daughter attends Highland Park High School. “We have the most at stake inside that building.”

District officials say there will be an increased police presence until the threat is diffused.

“While there has not been any physical threat directly to our students, the psychological impact of this on teachers and students is profound. It’s significant,” Kelly said.

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