'No conclusive answer': Officials still don't know what caused May intruder alarm at Maine West

Despite what officials called an exhaustive investigation, the cause of the false armed-intruder report at Maine West High School in May remains elusive.

"The in-depth internal investigation resulted in no conclusive answer on how the alarm was activated," Maine Township High School District 207 Superintendent Ken Wallace said in an email sent Thursday to families, employees and the media.

The May 12 alarm at the Des Plaines school prompted many students and staffers to flee the building while others barricaded themselves in classrooms.

Des Plaines police and officers from other agencies searched the building and found no threat. No one was hurt.

From the start, authorities said the alarm was triggered on the school's second floor. But it's unknown if someone accidentally or deliberately set off the alarm or if there was a mechanical malfunction.

School officials and police conducted interviews, reviewed security footage, examined specific locations in the school for evidence, tested the alarm system and even met with experts to learn about potential malfunctions, Wallace revealed in his email.

On Monday, while the building was closed, district officials and alarm experts set off the alarm to see if they could learn anything.

Although no cause was discovered, officials are confident the alarm wasn't triggered by a student - accidentally or deliberately.

Four fire panels in the building have buttons for an intruder alarm. Two are monitored by security cameras and two are in rooms accessible only by employees, Wallace said.

"If the button was accidentally or purposely pushed, it would have been from one of those two locations," he said. "We can say definitively that this was not a senior prank."

With the investigation complete, District 207 officials are making some changes to the alarm system, Wallace said.

Intruder alarm buttons will be removed from those four fire panels. Additionally, fire alarm panels will be locked to eliminate accidental activation.

Also, two-step intruder alarms will be installed in two key locations inside the building to prevent accidental activation. Both locations will be monitored by surveillance cameras.

District 207 officials are going to work with staffers to improve emergency responses, too, Wallace said. Communication between employees and with fire and police officials will be an area of focus. The district also will add training and reviews of safety procedures and equipment, Wallace said.

"We ... know we can improve," he said.

Reached Thursday, Des Plaines Police Chief David Anderson said his team had nothing to add to Wallace's report.