As others have reiterated, benzos are the best possible course of action here. Early 2008 I had an experience pretty similar to your friends, OP. I took two hits with a couple of friends on the same dose- i started losing it from those two hits and acting very out of character. In this state i then ate the other 8 hits we had sitting on the table (still in foil) as well as 3.5 grams of cannabis. As you can imagine, things got a lot worse.
This was in a remote area thankfully, and these guys were/are two of my best friends. Anyway, ambulance came, i went to hospital. Was generally unpleasant. I spent the next two years stupidly abusing psychedelics because i was convinced i needed to look for answers. 200+ trips at various doses later and i have never had a similar experience to the original one- the only factors i can think of that may have contributed to my episode were my age, an unfamiliar house, very high dosed hits (plus the other 8 once things had already gotten bad) and an evening with little sleep and DXM use the night before.
I was pretty torn up for a couple of years about wondering why this experience had happened to me. I realised i will never have firm answers but after reading several papers on psychotic reactions from psychedelics i have gathered that two of the most common factors are: high doses (obviously) and, interestingly, unfamiliar environments.
To answer your question, what you did was the best course of action. Without a sedative (and with no guarantee you would be able to administer it) you would have had to put him and yourself into harms way to restrain him, for who knows how long. It sucks to put your friend in that position but is better than causing lasting injury to either party.