I am most definitely NOT seeking to defend whoever left those dogs in the car. However I note that the incident occurred in a hospital car park. It might be (for example) that, having put the dogs into the car to take them for exercise, their owner got a call to say that their child had been knocked down and was fighting for life. He/she might then have rushed to the hospital and, in his/her panicked state, failed to make adequate provision for the dogs' welfare.
Equally (in a less dramatic scenario) the dog owner might have nipped into the hospital to do something which he expected would only take a minute or two (such as picking up medication from the hospital's pharmacy or to pick up someone whom he thought was already discharged but, as it turned out, wasn't). He could then have been distracted by, say, the pharmacist saying that there was a note on his file that he should speak to a doctor before collecting his medicine, resulting in him forgeting that he'd left the dogs in his car.
I repeat that I'm NOT defending the dog owner but I do know that the most diligent and caring of people occasionally make mistakes which they themselves find it hard to believe that they could have done. For example, some friends of mine were the most loving and caring parents that it could be possible to imagine, who would never do anything which could place their children in danger. However they got home from shopping in Asda (2 miles from their home) one day and suddenly realised that their infant son wasn't with them; they'd left him, sitting in his pushchair, in the Asda car park! If they could make such crazy errors, I suspect that we ALL can.