CHICAGO (CBS) — The Tinley Park mayor says officials have called every home in the village to let them know not to worry if they hear loud bangs around the property of the Tinley Park Mental Health Center.

It’s just an “urban warfare” exercise by the Pentagon.

WBBM’s Steve Miller reports, the U.S. Department of Defense has been conducting two days of training, which began Tuesday night and finishes on Wednesday.

It’s happening on the property of the now-closed Tinley Park Mental Health Center.

And what that most likely means is loud noises and helicopters.

Things Tinley Park residents may not be expecting.

“Over approximately a three-hour period, we called every resident in Tinley, about 20,000 homes,” said Tinley Park Mayor Ed Zabrocki. “We called each one to let them know what would be going on so that they understood what was being involved in this.”

Zabrocki said the perimeter road around the mental health center is being sealed off.

He said the Defense Department exercise is not for spectators.