The sniper who opened fire on an Immigration and Customs Enforcement field office in Dallas left behind notes saying he acted alone in an attack intended to kill and "terrorise" ICE agents, whose work he viewed as "human trafficking," officials say.

Although one person held in ICE custody was killed and two other detainees were critically wounded in Wednesday's bloodshed, it seemed clear from the gunman's writings "he did not intend to kill detainees or harm them," Nancy Larson, acting US attorney for the Northern District of Texas, said at a news conference.

No government personnel were injured in the incident, though officials said ICE agents and other federal officers rushed into harm's way to save some detainees sitting helpless in transport vans while shots were being fired.

The pe

See Full Page