Katy Perry is "devastated" about the death of her ex-boyfriend Johnny Lewis.

The "Firework" singer - who dated the Sons of Anarchy star for 18 months until early 2007 - is believed to have been partly inspired by her former partner throughout her career, but knew she had to break up with him at the time because he was a troubled soul.

"She is devastated. She had to separate from him to get ahead and focus on her career. He was in trouble then and she couldn't help him. A lot of her songs were partially inspired by him. I know 'The One That Got Away' and 'Circle the Drain' are partly about him, as well as Travis McCoy. But she was young and it was a time in her life she cherishes," a source told Us Weekly.

Johnny is believed to have killed himself by leaping off his home after beating his 81-year-old landlady to death. Police discovered the upstairs of the building had been ransacked and a cat had been killed.