People are finding origami butterflies with ominous messages, scattered on the ground throughout Seattle. The folded papers have a puzzling warning about safety, but no one seems to know who is behind the campaign or what it’s about.

When unfolded, the message “you are not safe,” is revealed and there is a date: 9-28-17. The flip side has illustrations of Russell Wilson, Kurt Cobain, the Starbucks siren, and a message about peace.

“It could be a marketing gimmick for an artist or something, I don't know,” said Henry Bridges, who found one of the papers in Capitol Hill.They are also showing up in the U-district, South Lake Union and downtown, and generating a lot of chatter on social media as people speculate about the motivation.

“I had some friends at Amazon say they're not going to go to work on the 28th, so, Amazon, if people aren't showing up on the 28th, now you know why,” Marc Shelffo, who also kept one of the papers, which he thinks started showing up this week.A website listed on some of the papers directs people to the same “you are not safe” message, along with the 9-28 date.Seattle Police said they hadn't received any calls about the papers, Tuesday afternoon.