BERWYN (CBS) — Morton West High School was placed on lockdown for a brief time on Wednesday for precautionary reasons after an unknown individual entered the building.

Berwyn police were on the scene.

Morton West High School is located at 2400 Home Ave. in Berwyn.

As of 1:20 p.m., the lockdown was lifted and normal school activities resumed.

“I was in lunch eating and I saw police ride around the street and then all of the sudden, they had Berwyn Police, Stickney, Lyons, Sheriff’s, all coming in with guns,” said Senior Pablo Fernandez.

When asked how many police officers he saw, Senior Kevin Jones said, “At least 30, maybe 40.”

And they came heavily armed.

”They had M-16s and AR 15s,” said student Ricardo Camarena.

Students Say they weren’t sure what was happening.

“I was actually in the lunchroom when three cops got there and they started showing a picture around and started looking for him I guess, Then more and more cars started coming, that is when they put it on lockdown,” said Ricardo Camarena.

“The teachers just told us, ‘Oh, we’re on lockdown now, we can’t leave class’ and there was only 10 minutes left of class and they just said, ‘Oh, it is probably a drill.’”

But this was no drill. Bomb sniffing dogs were even requested from the sheriff’s department.

Some parents say their children called them hysterical. In his classroom, Pablo Fernandez was calm but concerned.

“We saw the big guns come out that was when I was pretty worried,” said Fernandez.

But less than 90 minutes after it began the lockdown was over and classes resumed, leaving students with unanswered questions.

“All we knew is there was somebody like an intruder but we don’t know if they were a student or nothing. When they let us go, they didn’t let us know anything either,” said Richard Camarena

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