Without the original court transcript, it's wrong to go much further in to the details. The bottom line is that he was treated for gastroenteritis when, sadly, he had severe sepsis from pneumonia, which wasn't diagnosed for several hours due to a combination of systems failures, inexperienced staff, unfamiliar staff, over worked staff, and a short-staffed, under-supported, overwhelmed team, with poor supervision.
Much is being made of the possibility that the mother gave the child the enalipril, but frankly, that is the job of the admitting nurse and doctor to weed out that sort of information. "Is Jack on any medications normally?" "Oh yes, he takes x,y,z each day...." "Great, thanks for that." "We definitely wouldn't want him to have the enalipril when his blood pressure is so very low, so we won't be giving that one. Is it ok if we take his medicines while he's in, so that we don't get confused between who's giving what, or would you like to take them home? It's ok either way, but we'll need to make sure he's only given the medicines when they're prescribed on his medicine chart while he's in hospital
."