A man is being questioned over the murder of Daniel Graham who was stabbed to death in south London.
Mr Graham, 18, was knifed 24 times by a gang of youths as he got off a bus near East Dulwich railway station.
Police said the attack happened after trouble flared at Dulwich Hamlet FC clubhouse where up to 100 youngsters had gathered for a party last month.
An 18-year-old man was arrested on Wednesday morning on suspicion of conspiracy to commit murder.
A 15-year-old boy arrested on suspicion of murder has been bailed.
Mr Graham was among a number of people who left the clubhouse when shots were fired shortly before midnight.
Police have released CCTV images showing Mr Graham running towards the 176 bus and then getting off, into the path of his attackers.
Det Ch Insp Dave Manning, of the Metropolitan Police, described it as a frenzied attack in full view of dozens of people and appealed for witnesses to come forward.
On Friday dozens of officers were in the area handing out leaflets appealing for more information.