What is important to only say what your daughter would be ok with if she heard it. As teens, even 19 yo, what you say is likely to get back to her if they are friends of both of them.
Mostly, I say very little. I sympathize by saying something like I know this is hard. It is for both of them. Since you know him, I might say I've enjoyed knowing you. Saying he's a great young man is a bit condescending. Saying you"ll miss him may sound to your daughter that you're on his side. I stay out of my granddaughter's relationships. I know that this relation ship will be short term. I have fairly superficial relationships with boyfriends so that I don't feel a strong connection to them. I save the really getting to know him when they're both mature and on their own with enough exposure to them to know this relationship is likely long term.
This is her first boyfriend. There will be others. She needs to know that you stand behind her and won't get attached to her boyfriends. If you can be aware that a relationship is short term, that she is learning and will have other boyfriends. The purpose of dating is to learn what you want in a relationship and what you don't want.
Of course, she feels hurt and devastated. Support her by not talking about this boyfriend and deal with your own pain without involving her.
I would not call him. I,'d only talk with him if he calls or comes to your house.
Calling him puts him on the spot. And this.is between the two.of them.
You do know, that it's possible, even likely, that they will get back together.