Here's what I think happened....

After Jonny was dishonorably discharged from the army, he moved back in with his mom and began to drink heavily to cover up his failures. After getting three duis and spending six months in county, and becoming the "town drunk" and a blight on his family name, he moved to Hawaii because nobody knew him, he could hide amongst the tourists, and he didn't need to drive. His mom blamed herself and spiraled into a deep depression that ended with her suicide.