Ok what happen to bungie?

Ok i heard bungie had a problem but im not sure what it was. can some please infor me? cuz i saw the halo 4 trailer teaser and the develapors are 343 not bungie which confused me can someone give me a brief summary and link so i can read it as well cuz i have ps3 but i love halo so i want to knw thank u. :) are they making halo games still or did they get fired from microsoft or what.....yeah