Someone being able to contact a friend does not rule out mental incompetency.
I'm not speaking as a professional but as someone who was contacted by a schizophrenic friend shortly before he was involuntarily committed. He had no problem phoning me and described his situation and some of his plans quite eloquently. Mind you, he thought he was Jesus and was literally starving himself to the point of having to pin his briefs around his waist to keep them from falling off. I also spoke to his mother who had been leaving his favorite foods all around the house like someone trying to feed a deer and who was quite terrified by the way he had snarled at her.
In hind site, I am deeply grateful that his parents were able to lure him to his psychiatrist's office where he was detained peaceably. Had he been cornered in less controlled circumstances, where a knife or blunt instrument might have been at hand, who knows what would have transpired between him and the police. If he had been hurt or killed by the police, I could hardly be convinced that his being able to call me and to communicate so clearly with me would have meant that he was competent enough to know how to protect his own life in a moment of confrontation.
On a personal note, I am autistic. It is very rare for me, thank goodness, but I do sometimes have meltdowns in which I self harm in ways almost identical to those in the video. I worry about some day having a confrontation with the police, not because I am a law-breaker, but because of an episode of that nature during which I might be pretty dis-associative. Mind you, I would be able, shortly before, to call a friend and say, "I feel like I'm about to lose it. Can you come get me?" At that point someone verbally (or worse physically) getting tough with me can really push me over the edge and once a meltdown is underway it can also prolong the episode.
Outside of these very rare meltdowns I am perfectly reasonable and competent.
I volunteer at my local hospital where I always make a point of greeting any police or sheriffs deputies who come in, in hopes that they will come to know me and be more apt to give me the benefit of any doubts, as I am terrified of finding myself in some situation in which authority figures escalate a situation to the point of my being seriously injured.
BTW, that video makes me cry; it's so bittersweet.