Should I call a welfare check? Need help ASAP

Hi, I went through a messy breakup with my best friend/kind of ex. He has had problems with addiction and mental health and has let me known he has gone back to shooting up and has let me known he is at risk of dying (he has said not suicidal but has said death was a real risk now). He has also told me that he thinks people are out trying to kill him because he talked to strangers about his past problems and has heard through innuendos that people are hunting him down.

The whole thing is super complicated but I am extremely concerned for his wellbeing but hes said he isn't suicidal so I dont know if anything could happen from it and a welfare check could set him off or something. He needs to get psychiatric care, people in his life are telling him that and I am too.

We are no contact as of 2 days ago and I havent heard from him and dont have contact with his family or anything. He has no friends and no one to talk to and I am just so stressed worrying about his safety. Please let me know what to do. I dont know if this is "legal" but it involves the authorities so I dont know. Im freaking out

Location: Seattle, Washington