so this copilot is a complete scumbag. depression and suicide is nowhere remotely an excuse or even a valid explanation for selfishly mass murdering 150 innocent people.
While it's emotionally tempting to go with that opinion, I'm not so certain it applies. One thing about depression is that you stop caring and certain bits of your brain simply shut down. I think it is possible that this co-pilot, under normal circumstances and in a right state of mind would have been disgusted at the thought of killing so many people. But in the mental state of depression your emotion and empathy may cease to exist, maybe the passengers didn't even register in his thoughts when he took the decision to end his life, if that is really what happened.
It cannot be ruled out that he wanted to take all these people with him with malicious intent, but it can also not be ruled out that in that moment he was positively insane and didn't really know what he was doing.