Relationship advice?

So, I've been with this guy for 2 years officially but basically 4 all together, but his anger is a major issue. To the point where this mornjng be was screaming at me in public and threatening to beat my head in and that I wouldn't get back up, which is horrible. He keeps trying to apologise and it's not the first time his anger has gotten to be a problem and it's literally over stupid shit this was because I went on Instagram when I was at his and walked off from him cos I wasn't having an argument over something so stupid? He's 21 and I'm 19!! He's threatened me in the past and tried to use shit against me and when I've said enough is enough he says he's gonna go for a swim in the canal and drown! I don't know what to do ! He's currently seeing a therapist but tbh I don't think he's being honest with them