From search, it was originally reported at least 138 killed. It was good, for the million to show up on his tweet. Anyone claiming that mistakes don’t happen with today’s autocorrect, don’t use a cell phone to tweet.

At least 138 people were killed and hundreds more hospitalized from injuries in near simultaneous blasts that rocked three churches and three luxury hotels in Sri Lanka on Easter, a security ...

I can type love you, and if not watching, it will show up as -let be you-because my finger grazed another letter. Looking at the keyboard, the k is just above the m. If you accidentally hit mil, million pops up. My theory is he hit mil, realized his mistake, back tracked forgot the mi, million popped up, when he then typed killed correctly, not noticing what happened.
Admit it, it happens to the best off us.