Attorney Art represents Client Charles, the CEO of a promine…

Attоrney Art represents Client Chаrles, the CEO оf а prоminent tech stаrtup, in an active trade-secrets lawsuit against a primary corporate competitor. A trial date is set in 3 months. Last week, Charles scheduled an urgent, private meeting with Art. During the meeting, Charles was shaking and confessed, "I just took care of our problem. I hired a contract killer to eliminate the competitor's CEO. The hit is scheduled to happen this Friday night. Once he’s gone, their lawsuit dies, and we win by default." Art was horrified and immediately told Charles, "You need to call this off right now. I will not represent you if you go through with this.  I cannot keep this a secret." Charles became furious, and threatened Art, saying, "You work for me, and you're bound by attorney-client privilege. If you open your mouth to the cops or the judge, I will make sure you’re next.”  Charles then stormed out of the office. The next day, Art sent Charles a letter informing Charles of his immediate withdrawal from the case due to a breakdown in their relationship.  Art demanded Charles sign a substitution of attorney. Charles refused to sign.  He texted Art:  “If you try to drop me now, it will tank my company's valuation right before trial. I will kill you!” What are Art’s ethical obligations and options?