"So he was an agent for AQLV. Does that make AQLV responsible for everything that was done?"
Yes. He was the person in charge of the clinical study that AQLV "sponsored".
You will find the relevant legislation in Kenya and the US - and both laws apply to AQLV as a US Corporation conducting research in Kenya - makes the person coordinating the trial and the sponsor responsible for minimizing, reporting and trying to avert the potential adverse events of such a study.
AQLV/Mutisya didn't even apply for approval for the study, which would have been the first step in such damage avoidance.
They are not only responsible, but deeply culpable.
Again, that should be evident to anyone with a common sense of morality and a passing knowledge of regulations relating to biopharmaceutical research.