Russian leader Vladmir Putin has called the shootings in a school in Connecticut "particularly tragic" as the majority of the 28 killed were children.
The Kremlin said in a statement:
Vladimir Putin asked Barack Obama to convey words of support and sympathy to the families and friends of the victims and expressed his empathy with the American people.
More top news
Taha Hussain was 19 when he began sharing terror propaganda which said police and soldiers were among the "best of all people to kill".
Detectives have released CCTV images of people they want to speak to almost a year after Corrie McKeague vanished.
'Water Rats' gang leader killed after Briton murdered