London Borough of Hackney
David Smith, 20, was stopped and searched by Metropolitan Police officers in east London.
Around 80 firefighters were called to the fire on Monday night.
The aspiring musician was stabbed to death in Hackney in May.
A Section 60 order is in place for the whole of Hackney.
Mayor vows anyone caught with a knife would face 'the full force of the law'.
Collins, 25, apprehended by armed police in Rushden, Northants, on Saturday.
'This was a shocking incident that has left the victims extremely shaken.'