A second man is being questioned by police on suspicion of murder after the "sudden death" of a 30-year-old man in Cardiff.
James Way died a short time after being taken to the city's University Hospital of Wales on Sunday morning.
A 46-year-old from Grangetown, Cardiff, is being questioned, and a 42-year-old man remains in custody.
In a statement, the family of Mr Way from St Mellons said: "Our loving son James was so cruelly taken from us".
South Wales Police are continuing to investigate the circumstances surrounding an incident at an address in the Holmesdale Street area of Grangetown on Saturday.
Officers said Mr Way may have been involved in an "altercation".
He was taken to hospital at 0900 GMT on Sunday in an "unconscious state" but died shortly afterwards.
The family statement said: "We would like the public to come forward with any information to help the police in this investigation in which our loving son James was so cruelly taken from us.
"James was a loving, caring son and adoring father who would go the extra mile to help us and others. He will be greatly missed by us all."
Det Insp Mark Lewis, of South Wales Police's specialist crime investigation team, said: "The investigation is fast-moving and a team of detectives are working hard to establish exactly what has happened.
"It is believed that an altercation has taken place in, or near, Windsor Court at Holmesdale Street, Grangetown, probably some time between 4pm and 6pm on Saturday, February 19.
"If anybody saw or heard anything suspicious in this area, I would urge them to contact us."
Witnesses are asked to contact the incident room at Cardiff Central Police Station on 029 2057 1530 or anonymously via Crimestoppers on 0800 555 111.