TMZ reported earlier that he was rushed to hospital and that it didn't look good, and one of his training partners has posted on Facebook about his passing. Heart failure apparently. Nothing has been confirmed yet, but it seems that he's passed away.
EDIT: MMAFighting.com and Bellator have confirmed it's true. Kimbo has passed away.
http://www.mmafighting.com/2016/6/6/118 ... h-of-kimbo