From the gulit perspective I don't believe the crime was solely money orentiated
No, but it was a large part of it. He justified it to himself for the way they had pushed Suzette away, though he kept this concealed from Julie, telling her "they have forfeited their right to life for the way they have treated me."
Not happy in his job, not happy in his private life, he wanted to start anew, to break free from the prison inside which he felt incarcerated. But to free oneself from prison one first has to kill the prison guards..