Have I done the right thing?

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My daughter, 16, was dating a lad for about 10 months. This has now finished (he finished it) but since then the lad has become obsessed with DD. He self harms, not in an obvious way, but things like opening scabs and rubbing vinegar in, whacking himself in the shins with a cricket bat, things like that. He is threatening suicide to DD, and read out a pile of pills' names which he has stockpiled along with a bottle of vodka. He scared the absolute out of me the other night when I went out to the bins...he was hiding in the shadows in the pitch black and freezing cold in the hope of seeing DD. He's making her life hell at school, spreading lies about her and making her current boyfriend doubt her. He also kept texting me last week trying to tell me stuff that DD and her boyfriend had done; I wouldn't rise to it and he kept sending texts saying 'it's not my place to tell you what she was up to but you know what I mean...oh and please don't tell DD I told you'.
It's difficult because I am, or was, very close to him; I used to date his father and looked on him almost as a son.
DD e mailed his father last night and told him that his son was self harming, and threatening suicide etc...he didn;t believe her so I followed it up, saying that it was true, and that he needed to sit down and talk to his son as he needs help, he's hurting and in the process he's hurting DD.
The thing is, it's almost hereditary, or at least learned behaviour, as his father suffers serious depression himself. He once tried to throw himself off a motorway bridge, and has been under the care of the mental health crisis team for a few years now.
Have I don the right thing by telling him it's true? I'd want to know if one of my children was self harming or having suicidal thoughts. The lad has seen a psychiatrist already, about 2 years ago when his mum left so my fears for him are real, it's not 'just' a lost teenage love type of thing.
Any ideas?

I can't believe you're even doubting you've done the right thing. If he does attempt suicide and you were aware and had done nothing how would you feel? You absolutely have done the right in what you've done.
I would also consider talking to the school. This could be on the premise of protecting your DD but present all the facts including actual text messages and the school really ought to act.

Aubergine...thankyou. I have had no reply from his father as yet; the lad sent my DD a text last night asking her why she'd told his dad...she said because she had to and what had he said and the lad said 'well put it this way...you failed'. Can it be possible that a parent would ignore these warnings? I know I wouldn't. Yes, I am really angry at the way he is making my DD unhappy but it also through my own fear that he could be serious. It happens, teenagers do take their own lives. His Grandmother, who he was very close to, died in the New Year and he doesn't seem affected at all...which suggests to me that he is keeping a lot bottled up.

If you get anymore incidents contact the police with times and dates etc this is not acceptable behaviour and it needs to be delt with pronto

I have been really angry about it, but it's like having 2 different issues here. Firstly is my DD's happiness, and that of course is paramount. I fume when I hear what he has done and said. But then there is also the issue of dealing with an obviously troubled lad - he is so quiet and studious...if he was rowdy and lippy etc I'd pass it off (maybe) as teenage bravado, but he's ultra sensitive and I am so scared that he will go over the edge. And then that makes me angry too because I lived with my abusive and suicidal ex who regularly threatened/attempted suicide and made me feel responsible for it. I don;t want to have to deal with it again and I certainly don;t want DD, at the age of 16, to have to deal with it. The lad is just 15 BTW

Well apparently the lad's father is going to make an appt at the gp for a referral to CAMHS. He laughed about it to his son when DD's e mail reached him, but obviously thought twice when I sent one. Shame it took 2 people to point out to him how troubled his son is. Last time I saw him (the son)I was shocked at how much weight he's lost. The lad text DD and told her his dad was making him an appt. I have not had a reply to the e mail I sent; glad really as I don't want to have anything to do with him (he really screwed me over) but would have thought there would be some response. Anyway, as long as he gets the help he needs and lets DD get on with her life.