All hell ALMOST broke loose at a Kobe Bryant book signing in L.A. on Tuesday -- with cops responding to an upset crowd ... but sources at the scene tell us Mamba stepped in and diffused the situation.
Kobe was set to meet with 500 fans at Barnes & Noble at The Grove shopping center -- taking pictures and signing copies of his new book, "The Mamba Mentality: How I Play."
We're told everything was going fine until someone at the store let in an additional 300 people with less than 30 minutes left in the event.