Bellevue Police officers rushed to Downtown Park last night after receiving several 911 calls reporting someone screaming, expecting to find an assault in progress or some other mayhem. But instead, they stumbled upon around 100 people competing to catch ’em all on the new Pokemon Go app.

Pokemon Go is a augmented virtual reality game that uses the GPS on a player’s phone to detect where they are and make Pokemon “appear” around them. As with the very popular original playing card incarnation of Pokemon, players want to “catch ’em all.”

Since its release last week, hoards of people have begun playing the free game. Players have also started sharing information about locations with many Pokemon online, which is likely the reason why scores of people flocked to Downtown Park on July 10.

Residents living near Downtown Park told police they were hearing screaming from the park at 11:30 p.m. (the park, however, officially closes at 11 p.m.). Earlier in the evening, a crowd of Pokemon Go players had also run into an apartment complex in search of a Pokemon. Crowds also packed the park on Sunday afternoon.

It appeared that the players were engaged in some sort of virtual battle, police said.

An officer warned the players that the park was closed and that they had to vacate. No one was arrested, and the department is now warning players and parents to use common sense while playing the game.

“Just because you’re on an app and it tells you to go to a certain place, doesn’t mean it’s OK. If you were using your GPS and it told you to drive off of a cliff, you wouldn’t,” Bellevue Police spokesperson Seth Tyler told the Reporter. “People just have to use common sense and also make sure they’re being safe.”