Complex sentence: Later, Walter is shocked to learn that Hank is investigating Gale's (David Costabile) murder, Hank believing that Gale was the elusive Heisenberg and expressing regret that he was not able to arrest him.
Split into simpler sentences: Later, Walter is shocked to learn that Hank is investigating Gale's (David Costabile) murder. Hank says that he believes that Gale was the elusive Heisenberg and expresses regret that he was not able to arrest him.