A man has died after he was sprayed in the face with what police believe was ammonia.
Andy Foster, 26, was attacked by two people when he opened the door to a property he was inside in Eighton Terrace, Wrekenton, Gateshead, on Sunday 20 August.
Ambulances attended the scene at around 11pm and found him in a critical condition before taking him to hospital, where he died shortly afterwards, Northumbria Police said.
A murder investigation has now been launched.
A 26-year-old man was arrested on suspicion of wounding with intent to cause grievous bodily harm and was later released under investigation, pending further enquiries.
On Saturday night, the force announced five more people have been arrested as part of the investigation.
It said: "Officers have arrested 2 men - both aged 32 - on suspicion of murder. They have also arrested a man, 34, and 2 women - aged 37 and 30 - on suspicion of assisting an offender."
Mr Foster's family paid tribute to him as officers appealed to the public to help them find those responsible.
The family said in a statement: "Andy was such a kind and funny boy who was so loved by his family and many friends.
"He was our only son - as well as a loving and supportive partner, grandson and cousin - and was particularly close with his grandad who was very special to him. We are absolutely devastated and heartbroken beyond words that we have sadly lost our boy.
"Andy still had his whole life left ahead of him - and we are struggling to come to terms with the fact that he is no longer here with us.
"As a family, we would like to thank everyone in the community for their continued support and kind words over the past week.
"We now respectfully ask that we are given the time and privacy we need to grieve, as we attempt to process what has happened."
His next of kin are being supported by family liaison officers and officers are carrying out enquiries locally while trying to reassure the public.
Detective Inspector Tam Fowler, of Northumbria Police's major investigation team, said: "Our thoughts continue to be with Andy's family and loved ones at this extremely difficult time as they attempt to come to terms with their loss.
"While our investigation is at an early stage, we do believe that those involved are known to each other.
"Today, I am once again urging anyone with information - who has not yet shared it with police - to get in touch as soon as possible. Do not hesitate in sharing what you know so we can get justice for Andy and his family."