A suspect in the gun attack on police in the heart of Dallas told officers he was upset over recent police shootings of black men and wanted to kill white people, particularly police, according to officials.

A man opened fire on police officers responding to a domestic disturbance call in Pittsburgh, US, killing three of them, according to police department official.

The collapse of the World Trade Centre’s twin towers made 2001 the deadliest year for US law enforcement in almost three decades.