I've been away for a few years, but have returned as this tragedy is taking place in the country I call home. It's a pleasure to recognize some of your names and meet new members of our group.
If Lily and Jack wandered off on their own, they must have been terrified as time passed—likewise, if a stranger seized them.
Hideous as it is to consider, if they were purposely killed by an adult they trusted and +/ or loved, I can hope their deaths were swift and painless.
While none of us knows who or what caused the little ones to disappear, I'll be surprised if DM played an active part.