Nathalie Cros Brohan, sister of Mr Thomas's girlfriend Christine Delcros, posted on Facebook this morning that the family "fear the worst".
His girlfriend, who was hit by the vehicle, is seriously injured in hospital.
People gather during an event for the victims of Saturday night's London Bridge terror attack.
Police on Tuesday identified the third attacker in the weekend terror assault in London amid mounting anger, two days before an election, over how the jihadist killers had apparently escaped surveillance.
The 30-year-old was held on suspicion of the commission, preparation or instigation of terrorist acts during a search of a property in Ilford and taken for questioning at a south London police station, Scotland Yard said.
Battlefield 1 In the Name of Tsar s'offre un teaser
Si vous possédez une autre plateforme de jeu, vous pourrez également vous procurer Battlefield 1 puisqu'il est disponible sur console également.
Police killed all three attackers.
Police disclosed late on Monday that 27-year-old Khuram Butt, a British citizen born in Pakistan, was known to police and domestic spy agency MI5, but with resources scarce had not been deemed enough of a threat to warrant close monitoring.
Police have made more than a dozen arrests in the wake of the London Bridge attacks, but most have now been released without charge.
The report said Italy had put him on a watch list and flagged his presence to Moroccan and British authorities.
Collina said Zaghba was monitored by Italian intelligence agents each time he came to Italy to visit her after that initial run-in with authorities.
The leaders said they would not carry out the ritual that is normally performed for every Muslim, regardless of their actions. Both men lived in the Barking area of east London.
The attack, and prior attacks in Manchester and near Parliament in London, have prompted Prime Minister Theresa May to call for tougher counter-terrorism laws even if it means changing human rights protections.
- Vettel fastest as Ferrari dominate final practice
- Turkey's Erdogan Dismisses Charges Qatar Backs Terrorism, Pledges Aid
- Best iOS 11 Features That'll Change Your iPhone And iPad
- Theresa May to finalise cabinet amid DUP talks
- India Beat Pakistan by 124 Runs, Man of the Match Yuvaraj Singh
- Cavs' Irving inspired by Warriors' talk of celebrating at Cleveland
- Watch Simona Halep vs Jelena Ostapenko on TV, online
- Microsoft tease et fait monter la pression avant l'E3 — Xbox Scorpio
- Trump says Comey testimony showed 'no obstruction'
- Privée de sa majorité absolue, May reconduit son gouvernement — Royaume-Uni