It was hours before medics entered a courtyard where victims were stabbed in the London Bridge attack.
Several contenders criticise Donald Trump for his attacks on Sadiq Khan as they answer journalists' questions.
Rebecca Bryant's son's partner was a juror in a murder trial where she was the family liaison officer.
The US President dubbed Mr Khan a "disaster" following a spate of violent crimes in London.
The child was on holiday in Kos with his family from Merthyr Tydfil, south Wales.