A man was stabbed to death yards from his front door in an attack by a mob of up to 40 youths on bicycles.
Jason Gayle-Bent, 29, was sitting on a wall with two friends when the gang rode up in Ludwick Mews in south-east London on Sunday, police said.
One of the youths pulled out a gun, aimed and fired several shots before the group dispersed.
Police believe the same gang may also have attacked and wounded another man shortly afterwards in Deptford Wharf.
Straight after the attack on Mr Gayle-Bent, the gang is thought to have fired shots in the air outside the Community Action Centre in Grove Street.
Police believe they then chased a man who fled the centre on a moped. In his bid to escape the gang, he crashed his bike and then tried to run off.
The youths caught up with him at a doorway of an address in Deptford Wharf, where he was assaulted and stabbed.
A firearm was also discharged at the scene. The victim was treated in hospital and has since been allowed home.
Police are investigating whether the two attacks were linked and are keeping an open mind as to the motive.
More today - again I haven't heard anything on the news.
More than 2,000 pupils were sent home early on police advice, after threats of gang violence outside two schools in south-east London.Gang threat shuts schools early
Pupils at the Peckham Academy, Peckham, and Harris Girls' Academy in East Dulwich were sent home at 1400 BST.
Police advised head teachers to end the school day early and said they would step up patrols over the weekend.BBC London correspondent Guy Smith said it could be linked to the murder of a man in nearby New Cross on Sunday.