My son fell off the second floor

Okay so we moved into some apartments about five months ago. I have my apartment completely baby proof! He can’t get out the front or patio or windows. That’s my biggest fear! Well there’s a closet with a water heater inside of it. And I guess there was another small door behind the water heater! To top it off the door just pushes open. Yea mybad for never noticing that second door behind the water heater. I would never think they would have a random door behind the water heater upstairs! Mind you the water heater is in this closet in my hallway. Anyway I was paying my bills I thought my son was in his room and I just hear him crying. I have no idea where he is. It sound like he was in the closet with the water heater. So I open it and see the light to the other door. And he’s on the floor downstairs standing up crying. My heart dropped. Luckily he had no scratches or bruised. I took him to the er and he is fine. I am so mad that the apartments wouldn’t have that area more secured. And why they have an Unecessary door!!! I can’t stop crying my son is only 2. Just needing to vent