Seven people have been arrested after a man was stabbed to death in the street.
A 24-year-old man was found with serious stab injuries in Maidenbower, Crawley at about 18:30 GMT on Thursday and died at the scene, police said.
A man, 47, and woman, 44, were arrested overnight for conspiracy to murder and a man, 20, was held on suspicion of murder and a drugs offence.
Three 17-year-old boys and a 24-year-old man have also been detained on suspicion of assisting an offender.
The man who died has not yet been named but his family have been informed.
Det Ch Insp Till Sanderson said: "We believe that the victim was known to his attackers."
Two brothers told the BBC how they tried to resuscitate the injured man and gave him CPR until paramedics arrived.
Hugo Sousa said: "I was on my way to cadets and I hear my brother shout 'help someone's been stabbed', so as a cadet, I ran over, tried to assess the situation.
"I saw a few punctures and I immediately started doing CPR on him until the paramedics came and then paramedics came and then I left."
His brother, Paulo, said: "We heard that he was gasping for his breath 'help me', [he] repeated it four times.
"We laid him flat, gave him CPR and then paramedics eventually took over and we got told he didn't make it."
Sussex Police said officers were looking for another person over the murder.
All those arrested remain in police custody.