My cousin has himself and others in serious danger

[irrelevance]

My cousin is almost 19, and has been a rather depressed type of person pretty  much his whole life. His upbringing wasn't great, his parents have a very disagreeable dynamic, and divorced a few years ago, and both are with other people. And both have their own domestic issues he receives money from both parents. He started to turn more to drugs , I do not know how long ago.. but all I know is that he does many different pills, and drinks.  He has always talked about suicide, joked about it, and just brought it up more than the average person.  Obviously thinks about it a lot. I guess being the typical 'tortured soul' of a musical artist, most just wrote it off for a while, or didn't know what to do.

NOW, I am hearing for the last couple months he has been saying when he gets mad and throws his little tantrums, he goes off at the drop of a hat.. so we hear his threats of suicide, but recently has added that he wants to kill as many other people as he can, when he goes.
This is rather concerning.  Especially on a personal level considering I have been on his 'list' for quite some time now..
Just yesterday the family catches wind that he has just bought a hand gun.

Is there anything at all I can do?  Is there any institutions (Ohio area) where you can forcibly admit a person, with  no willful leave, on account of being a danger to himself and others?  I know I have no proof of this, and the cops can do nothing.
What do I do?

I don't want to just sit back and wait for the day to come... And I honestly feel as though my life, and those of my family members is truly in danger. And even if you set that aside, he is clearly a danger to himself.

[Peter Forster]

You should contact the local mental health center in the area where your cousin lives. I think that your concerns should be followed up on. Please let me know how you do with this.

[Jaquta]

As far as I am aware as long as a person is a risk to either themself or others they can be committed for assessment and treatment.

You could phone your local mental health services and ask for advice or call your local police.  I think that most hospitals have secure psych units attached to them.

It sounds as though your cousin has an underlying psychiatric condition.

I think that safety issues should be treated with some sense of urgency.  At the very least it can be someones way of communicating their distress or a way to ask for help.