How do I get my brother into a treatment program if he is unwilling to go voluntarily?

My brother is addicted to meth and is also suicidal. His common law wife found out that he was having an affair with another women who is also addicted to meth. Since then my brother talks about killing himself and he has a loaded gun that he carries in his pocket. His wife has told me that he has held the gun to his chest and head in front of her threatening to kill himself for what he has done. He also says that he is obsessed with this “other women” and can’t let her go. They apparently have had a very volatile relationship and this other women knows how to push his buttons. He seems even more obsessed with her since he found out she has another boyfriend. She continues to call my brother and even met him at a motel last monday. My brother said they did some meth together then somehow she drugged him and stole his car (the car he was driving belongs to our dad). Since then he is delusional and even more suicidal. During one episode he kept calling his wife by the other girls name.