What he recognized of the symbol would depend on how much he has the ability to figure out what demonic arcane symbols from Piper's world might mean. Either way, it was definitely something designed to drain the life force from non-magical beings... humans.
Piper looked a little confused as she studied the paper as well. There was some strange writing on it. She took out her cellphone... a simple little flip phone that probably had a really lame camera on it, but she tried to take a picture, hoping there wasn't any magic to prevent it from showing up. She had already done the same for the stuff on the ground.
This was the best she could do in the circumstances. And now, she needed to get out of here before anyone else showed up and tried to call the cops. Without any allies remaining at the precinct since Daryl left, it was harder for her and her sisters to avoid getting tied into incidents like this in a bad way.
She pocketed the small phone and turned just in time to see Nico. She raised her hands for a moment, ready to freeze him if she needed to.
"What are you doing here?" she demanded, clearly not recognizing him off the bat.