Speaking the Evening Standard, Catherine Seale urged parents to make sure their children check their privacy settings on Facebook.
The last thing I told him before I went away was 'don't have any parties'.
They could have been killed. Even though it had been cleaned up when I got back from France, everything felt sticky and dirty and it stunk.
There was vomit in the sitting room, cushions were completely ruined, and the sofa stank for days.
All parents should be warned that this could happen if you go away and leave your 17-year-old alone.
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"All it takes is for somebody to see me - and I could just die, just like that. I could want to go to the shop and not come home."
Before the killing, Peters searched the internet for "serial killers", "treatment of child killers in prison" and "premeditated murder".
Arriva Rail North, Greater Anglia and South Western Railway are all affected.