Parsons Green tube station
He was killed near the scene of last month's terror attack.
Omid Saidy lost life for asking drug dealer to move on.
Scotland Yard says one of injured men has been arrested.
18- and 21-year-old remain in custody.
Operation comes after Dover arrest.
The 'bucket bomb' is believed to have only partially exploded.
'This poor little boy had his face smashed in and he was screaming.'
Witness tells HuffPost of 'horrendous human pile-on' as people fled.