why are my children trying to kill me

i found my son henry at the top of the steps this morning.  yes he was teetering on the top step.  i heard him wake up on the monitor and he was fussy.  usually if he wakes up fussy he goes back down. well he fussed and then nothing.  the next thing i hear is something tumbling down the stairs and hitting the baby gate at the bottom of the stairs.  i shoot up and THANK GOD, i see him standing at the top and not at the bottom.

i didn't even hear a thud from him getting out of his bedding- nothing!  needless to say, we will have two gates on our stairs.  my heart just stopped when i heard something falling down the stairs.