Nice attack: What we know so farReuters

A man who lost six members of his family in the Nice terror attacks has been left so traumatized he is unable to speak. Christophe Lyon's wife, his adult son, his parents and parents-in-law were all killed on 14 July, when Tunisian-born Mohamed Lahouaiej Bouhlel drove a 19-tonne lorry into crowds of revellers celebrating Bastille Day in the southern French city.

Lyon, from Longwy, north-eastern France, had travelled to Nice with his wife Veronique, 55, son Michael Pellegrini, 28, and in-laws Francois Locatelli, 82, and Christiane Locatelli, 78 for an eagerly anticipated holiday on the Riviera. His parents Gisele Lyon, 63, and Germain Lyon, 68, also joined the family gathering.

Michael, Christophe's son from a previous relationship, taught economics at a local sixth-form college. A colleague of Michael said he was "overjoyed" to be attending the Bastille Day fireworks display.

Lyon's elderly parents and in-laws were enjoying their retirement life and had been looking forward to a family holiday. Germain and Gisele had taken an extended trip to the Côte d'Azur, spending several days in Marseille before joining their family in Nice Mirro Online reports.

All six died as they were struck by the lorry which was driven at high speed for over 100 metres, 'zig-zagging' through the crowd. The truck driver was eventually by police.

At least 84 people were killed in the massacre, among them 10 children, with another 202 injured – 52 of them seriously. 50 children were said to have been taken to hospital with some of their relatives still not found.

Islamic State (Isis) claimed responsibility for the truck attack, as French police arrested five people in connection with the massacre. France has begun three days of mourning as the investigation continues.