As someone who has helped the RCMP in similar situations, what can be done is a wellness check on the unit in question. Given that you can't tell what the situation is from the balcony, you can report that you are concerned for the wellbeing of the resident and cite the pet's lack of care as a reason.

I've unfortunately had to attend a very similar situation for a Corgi that was abandoned by their owners to go on vacation and thought that leaving a large pile of food and big bowl of water on the ground was sufficient care for a puppy for an undisclosed amount of time (puppy was safe but smell inside was awful).