Baton Rouge gunman signalled 'horrendous acts of violence' in manifesto

The man who ambushed and killed three law enforcement officers in Louisiana reportedly called his actions a "necessary evil" in a handwritten manifesto that an Ohio man says was emailed to him by the gunman less than an hour before the shootings.

Photographs of the three-page letter show it was signed by "Cosmo", the first name of an alias used by Baton Rouge gunman Gavin Long, and the pictures were attached to an email sent from a Google address Long used.