Since 9/11, Islamists have killed about half as many people in the US as white extremists
Adam Lanza went from buying toys for needy children to a mass murderer, says father Peter
Connecticut gunman called college station to discuss Travis, a chimp that 'ripped woman's face off'
Adam Lanza wrote book about children being slaughtered years before carrying out murders
Reece Elliott sentenced to 28 months in jail after Facebook threats sent US schools into lockdown
Jim Carrey's objection to violence in his own film 'Kick-Ass 2' has sparked a wider debate
Does US senate's rejection of tighter gun laws mean memory of Sandy Hook massacre is fading?
Names and faces of those caught up in the carnage are revealed as hunt for perpetrators gathers pace
Patriots' Day bombs leave three dead: setting and timing could point to right-wing causes