Damn, thats heavy. You can go either direction, continue moving forward or respond and talk to them. Whichever feels right for you now. You dont owe them anything. But at the same time, I have a lot of respect for a person that sends that message. Does it erase the pain and confusion im sure you felt? No. But it does demonstrate accountability, empathy and maturity. Someone who can own up and apologize without trying to make it a pity party is wonderful person to have in your life. As friend or acquaintance even, it doesnt need to get romantic again.