Killian committed suicide at his computer; his suicide note informed Hansen that he had stolen the Extremis serum for an undisclosed purpose.

Did Aldrich Killian die?

When Killian was blown up the first time, he took a lot of damage, but it seems that his body mostly stayed in tact. The second explosion by Pepper, as Elfangor states, was probably too much for Killian's body to handle, and he died.

Is Aldrich Killian Fin Fang Foom?

Fin Fang Foom – Guy Pearce's character Aldrich Killian has a tattoo of a dragon on his chest. The dragon tattoo is likely a reference to Iron Man villain Fin Fang Foom.