Your daughter needs to take good care of herself first.
Not knowing him well ("new boyfriend"), she might do well to decide to see him only in safe, public places. Who really knows what's going on with him -- could be drugs, bipolar, other?
He may benefit from his friends clearly telling him he needs help, asking him to go to the ER.
If there's a way to alert his family, doing so may be helpful. They may have some background info. which may be helpful and/or they may be able to appeal to him.
Thank you for your concern for your daughter. I am sure his behavior is confusing to her. I'm sure she'd like to respond in a helpful manner. Yet, who knows what's truly going on with this young man? He really needs an urgent medical/psych assessment.
My heart goes out to all parties involved.

Wild Coyote