Mom saves toddler from falling off building

In a heart-stopping CCTV footage, a mother can be seen rescuing her son, moments before he was about to fall through an apartment building stairwell. The incident took place when the toddler wandered off towards the stairwell while his mother waited for the access door to be opened. The child then proceeded to stand on the stair railing but as there was no glass he slipped through. His mother springs into action and catches him by the leg before successfully pulling him .