"He was a quiet, nice kid who had banter with people. He was just a nice kid. I have seen some reports that say he was bullied but it was just banter - he gave back as good as he got."
Scotland Yard said the incident is being treated as possible terror offence.
Friday's explosion on the London tube is the latest in a string of terror attacks in the United Kingdom in recent years. Here is a timeline of the terror that has unfolded in the UK.
The two "terrorist incidents" at London Bridge and Borough Market on Saturday night are among several attacks that have taken place in the United Kingdom in recent years.
Vandals on Monday defaced a memorial to the victims of July 7, 2005 London bombings hours before survivors and relatives were to gather there to pay tributes on the ninth anniversary of the attack.
Survivors of the attacks and relatives of the victims were among those to mark the 10-year anniversary at a ceremony at St Paul's Cathedral in London.
The threat from terrorism continues to be as real as it was ten years ago, but Britian will never cowed by it, Prime Minister David Cameron said on Monday.