Grenades Around Chicago

The Tribune is reporting that Chicago police found a military grenade inside Wrigley Field this morning. It didn't contain explosives and no injuries were reported but the bomb & arson unit is investigating. The M12 grenade was found on the right-field side of the park.

You know, people throw balls back into the field.. but grenades... but then again, the cubs did let a lot of fans down this season.

Last week police were called to the scene of a small rubbish fire on the Southwest Side, a block from Midway. Nearby they found a grenade attached to a propane tank with a fuse, homemade bomb style.

So are these instances coincidences? Or is someone peppering Chicago with grenades?