Fission, like the a-bomb used on Japan, is breaking atoms apart, making smaller atoms. Fusion is making elements fuse together to make different (bigger and heavier) elements. Both processes liberate energy. Fission is not a natural process. Fusion is natural and happens in the stars, like our sun. Supposedly, all of nature's elements heavier than hydrogen were formed by fusion inside stars.
The processes are not similar, although a fission reaction is used to trigger fusion in a hydrogen bomb. http://www.diffen.com/difference/Nuclear_Fission_vs_Nuclear_Fusion
The scientist that died was one that claimed discovery of cold fusion decades ago, not Rossi, the "inventor" of E-cat cold fusion.