HOW did an 18th birthday party in the suburbs of Sydney turn into the scene of a “frenzied bloodbath”?

That’s the question police are attempting to answer as investigations continue into the apparent murder of a teenage boy who was one of seven people stabbed when a house party turned violent.

So violent was the fight that witnesses have described “screaming and blood everywhere” after a fight lead to a group of drunken youths producing killer weapons.

Ryde Superintendent John Duncan described the scene police arrived at as “confronting” as drunk youths paraded around the party.

Though NSW Police is remaining tight lipped on all aspects of the incident, reports suggest 16-year-old Aidan Smith was with a group of friends when they heard “someone wanted a fight” at the party in Ryde, in Sydney’s northwest.

Though Aidan’s sister has slammed reports her brother attended the party looking to get involved.

Nova Smith posted her anger at the reports overnight, claiming Aidan was “celebrating one of his best mates 18th birthday at his house and did NOT ‘travel to the house knowing there was a challenge’.

“He was simply in the wrong place at the wrong time,” she wrote.

Other friends described the reports as “a load of sh*t”.

The party was taking place at a ‘halfway house’, and about midnight on Sunday, Smith and his friends apparently made their way there. Not long after, a fight took place, and reports suggest a dozen weapons were produced, leaving six males and a female injured.

Aidan was among those injured, and despite undergoing “emergency surgery for deep puncture wounds”, he died at hospital yesterday.

Police say they’re still unsure how the fight erupted, and why, and “inquiries are continuing” until homicide detectives crack the case, they told news.com.au.

Even the type of weapons used is unclear as authorities question the 50 partygoers.

“Everyone was just talking and having a good time and there was not any trouble. I do not know how it happened,’’ a partygoer who returned to the house yesterday to retrieve some clothes told the Daily Telegraph.

Police were called to the home just after midnight and found six males, including Aidan, and a female with stab wounds.

Another 16-year-old male remains in a critical condition while a 20-year-old man who was also stabbed refused treatment.

The injured included three 16-year-old male, a 17-year-old male, a girl aged 18 and a 20-year-old man.

An emotional tribute was written by sister Nova after the devastating news.

“I love you with all my heart Aidan and I’m so sorry this had to happen to you,” she wrote. “R.I.P. my baby brother still cannot believe this has happened,” the 21-year-old wrote on social media.

No one has been arrested or charged over the fatal stabbing rampage and several people are being questioned as investigations progress.

Supt Duncan told reporters the matter is being treated as a homicide.

“At this stage of our inquiries we are trying to establish why the party turned violent,” Supt Duncan said.

“A number of people left the party soon after the fight broke out. Our inquiries are continuing and we hope these people will contact Crime Stoppers.”

The house is a rental managed by My Foundations Youth Housing Ltd, a community housing provider which acts a the landlord for a number of similar properties offering affordable social housing for young homeless and other vulnerable people, CEO Rebecca Mullins confirmed.

“We manage a range of different types of housing — some longer term where people live with us for up to five years and pay affordable housing rates or graduate to full rates over time, and also some specialist homeless services housing — not short term — usually up to 12 or 18 months,,” she said.

Ms Mullins said My Foundations Youth Housing was unaware of the incident until 11.30am Monday.

“As to the actual event, I can’t add anything for you,” she said.

“I can confirm we do manage the property, and I’d add we are really saddened by what has happened.”

“We are a housing manager, not a support agency. There’s a police investigation proceeding, and we are subject to the laws of the NSW Residential Tenancies Act and the privacy that entitles tenants to.”

She could not comment on whether any of the tenants was among those injured.

But she said she was not aware of any complaints being made about the house’s tenants previously: ‘Not to my knowledge, ever since we have managed it’, she said.

“I did see in some of the reporting that neighbours were saying the same thing.

“It is an awful event, but there have been no previous complaints about that property.”

— Do you know more? Email youngma@news.com.au

— Additional reporting by AAP