A man has died after being stabbed in the chest in Sydney's northwest while police have charged another man over the fatal stabbing of a teenage boy.
The 28-year-old from northern Sydney was found in a critical condition at Narcissus Avenue in Quakers Hill on Friday evening.
"About 8.30pm last night police were called to an address in Quakers Hill where they found a man who had collapsed on a porch of a neighbour's address," Detective Superintendent Scott Bingham told reporters on Saturday.
"Police found that that man had suffered a stab wound to the chest.
"They rendered first aid and an ambulance arrived shortly after."
Paramedics worked to save the man but he died en route to hospital.
Police are not considering the attack a random event.
"This man has known the people in the house and we believe it occurred inside a nearby premises," Det Bingham said.
"We have a number of detectives and other personnel down searching the address and searching the nearby streets."
Police have asked anyone with CCTV footage, dashcam or information about what happened to come forward.
No one had been arrested in relation to the incident by Saturday afternoon.
In a separate investigation, police charged a 26-year-old man on Saturday night after a teenage boy died following a stabbing in the state's west.
Emergency services were called to a home on Nymagee Street, Narromine at 9pm on Friday.
Officers arrived to find a 16-year-old boy with stab injuries to his neck.
He was treated at the scene by NSW Ambulance paramedics before being taken to Dubbo airport where he died.
Following inquiries, police arrested a 26-year-old man at a home nearby.
He was taken to Dubbo Police Station where he was charged with murder.
He was refused bail to appear at Dubbo Local Court on Sunday.
Det Bingham said NSW Police had been running multiple operations focused on knife crime.
"No one should be carrying a knife in public," he said.
"If you're caught with a knife, there are substantial penalties."
