Fair enough, it does sound like he's having some pretty severe mental health problems from those additional details. I care for your friend, if you can relay some of this advice to him when he's feeling better, it would be beneficial.
To echo other people in this thread, you're not responsible for him, but if you have the emotional bandwidth to help out where you can, you can make a difference in his recovery outcomes. It sounds like a lot of pressure, but the more relaxed and detached you are the better it'll be for both of you.
I generally think you were completely right to call the mental health team, but he understandably might still be angry.
I care for your friend, and here are some concrete steps that worked for me, in order of effectiveness.
1. Taking time off work, or even leaving if that's possible
Sounds like workplace tensions caused or exacerbated what he's going through. It's likely his mistrust has spiralled into some kind of paranoia. It's also possible that workplace stress is exhausting and destabilising him. It's best for him to simply take extended leave, or leave the workplace entirely.
2. Avoiding psychiatric labels in favour of therapeutic/psychological labels
Understanding that paranoia develops from suspicion, and suspicion grows from fear, and fear grows from mistrust. To elaborate, it sounds like he's having some kind of conflict where he thinks other people are doing x or y to him, but that's likely just mistrust spiralling out of control. One attitude is to label this paranoia, and as a psychiatric symptom of psychosis/schizoaffective disorders, another attitude is to label it as an extreme version of mistrust. Both are true, but one is more conducive to healing. Basically, if I were your friend, I would avoid internalising any labels he would be taking on during this period, because that can actually reinforce negative outcomes.
3. Eating pure, unprocessed, and heavy foods.
A lot of mania like symptoms are just the result of emotional or mental exhaustion. That causes us to get light headed and start overthinking, and then have an emotional reaction of fear, which causes more overthinking and so on, which can spiral out of control. A simple solution that doesn't involve pharmaceuticals is drinking lots of fresh, spring water, eating tuber and root vegetables like potatos and carrots, and also fatty and greasy foods like cheeses and butter. Basically, natural and whole foods which weigh you down, not things like McDonalds or potato crisps. Drugs are likely going to be necessary for at least a couple of weeks and maybe several months, but longer than this, in my opinion is likely detrimental to the brain's physiology. Your friend sounds quite intelligent, let's keep it that way.
4. Sleeping more
Like I said in my previous response, lack of sleep can cause and exacerbate mental health problems. Sleeping drugs or aids like melatonin may be necessary at this stage, but if not, then natural remedies like camomille tea, a relaxing bath and music would help.
5. Working with a psychologist/therapist, rather than a psychiatrist
This perspective may be polarising, but I believe that psychiatrists are not equipped to help heal severe mental health issues. At best, they are a temporary support that prescribes medication (which is necessary initially for weeks and months). To end up on medication for years and decades, and stuck with a psychiatrist who keeps on prescribing them is a one way road to being a zombie. Instead, in my opinion, working regularly with a psychologist and/or licensed therapist is the best way to recover from so called severe mental health illnesses like bipolar/schizoid disorders. If your friend has the financial means, additionally working with a neurologist once he's more stable (maybe 1 or 2 months from now), would be even better. The neurologist can rule out things like actual physical brain conditions like high cranial pressure, brain tumours and other physiological causes of mental health problems.
6. Spending time in nature during the day, either alone or with a trusted friend
Just sitting or walking around in a park can have extremely outsized benefits for mental health. That means going to as secluded and natural of a place as is practical. If there are no people in the place, that's even better. I experienced it myself, when I walked in a park every day and recovered extremely quickly.
7. Having the intention to surrender to a higher, benevolent power
Your friend is communicating with voices in his head, which is a a big warning sign, from a spiritual, psychiatric and psychology perspective. It could be anything from different parts of his psyche communicating to try and come to a resolution, or it could even be what are called "jinns" or negative spirits in religions like Islam. While many may roll their eyes at the mention of spirits, especially in a more secularly oriented community like Hacker News, this is a possibility. The solution, regardless of what is happening, and regardless of what you (or I) believe is happening, is surrendering to a higher power. It could be surrendering to God, Allah, Buddha, Earth, Universe or the Void. It doesn't matter whether he's atheist, agnostic, religious or spiritual, simply having the internal intention to surrender to a higher power will deliver very rapid healing and peace. If the intention to surrender is genuine (not laced with doubt or skepticism) and comes from a deep place, it will cause an instant effect of peace and relaxation. You can even try this yourself right now to verify it. It definitely did for me. In fact, this last point was the most effective, over everything else I mentioned.
If your friend wants to talk to someone when he's feeling better I'm always available.