I've actually been wondering how the bomber was able to acquire the addresses of top Democrats and celebrities. He had to have access to some kind of political mailing list.It's now being reported that he is a career Democratic staffer who was since cast out two years ago for being too extreme. He's been unemployed since. Papers found in his home indicate he multiple objectives: get revenge against what he considered to be hypocritical corporate/establishment Democrats he blamed for his plight, inspire sympathy for the Bernie Sanders/Occasio-Cortez branch of the party, and sabotage Republicans chances in the election.
Simple searches on the internet. No big deal to find any address.