Authorities have apprehended a fired worker who is accused of threatening a shooting in Kansas City’s massive subterranean network of businesses housed in old limestone mines.

Police said Tuesday in a tweet that they found the worker in Kansas City, Kansas, and lifted the lockdown at Hunt Midwest SubTropolis in Kansas City, Missouri. No other details were immediately released about the capture, including the worker’s name.

Police said earlier that security spotted the worker entering the cave system after he said he would “shoot the place up.” Numerous federal, state and local agencies helped search while workers were told to stay inside their locked offices.

Many of the businesses in the cave system specialize in storage or warehousing because they are protected from extreme weather and boast stable, year-round temperatures and humidity.