UnScramble this Word: l c e n a m p a?

Questions

Which singer died an unhappy man when his father shot him in 1984?

Whose equations first suggested that mass and energy are interchangeable?

From which musical did the songs 'If my friends could see me now' and 'There's got to be something better than this' come?

What did Hercules use to clean the Augean stables?

Who wrote the thriller "The Bourne Identity"?