The names of 20 children and their six teachers were read out today, six months after they were shot dead at Sandy Hook in one of America's worst school shootings.
Since the school massacre, thousands more people have died from gun crime in the US.
The parents of the children killed in December are still fighting for a change in gun laws.
This report is by ITV News Washington correspondent Robert Moore:
A special Tonight: America and its Guns was broadcast at 19.30pm on ITV
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Harry will also pay tribute to a British soldier killed by an elephant during anti-poaching operations in Malawi.
The family are making an official visit to South Africa.
The duke, who has admitted “I feel more myself in Africa”, is about to begin a tour of South Africa with the duchess and Archie.