A 15-year-old boy has been arrested on suspicion of murder and arson with intent following the deaths of an elderly Warwickshire couple in Rugby.
Kath and Albert Adams, both 77, were killed when a mobility scooter parked outside their home in Rugby was torched and the blaze spread to their sheltered housing complex.
The teenager was on Tuesday night being held in custody where officers were questioning him, Warwickshire Police said.
Police said the fire on Saturday was being connected to a second blaze at the same flats on Monday morning, which also involved a mobility scooter but left nobody injured.
Earlier on Tuesday, the couple's family paid tribute to their memory and urged the public to help catch their killer.
Relatives described the 77-year-olds as the "rock" which united their family. In a statement issued by Warwickshire Police, the pensioners' family, including their son Keith and daughter Nicola, said: "Kath and Albert were a lot of things to a lot of people - parents, grandparents, brother, sister, friends.
"They were really loved by their family and were the rock that pulled everyone together. Their tragic deaths have left a massive hole in our lives - that pain will never truly fade."
The statement continued: "Their door was always open and their children and grandchildren knew that all problems could be solved with a spoonful of rice pudding and copious amounts of tea.
"Despite their ill health in recent years, their cheeky sense of humour never left them - nor did Kath's love of shopping and Albert's love of football."
In their statement, the family said they had no knowledge of disruptive or anti-social behaviour in the area around the couple's home in the sheltered housing complex in Harold Cox Place, which they described as a "lovely supportive environment".
Detectives launched a homicide investigation on Monday after a second fire broke out near the Adams's home. Officers believe both fires were started deliberately and are connected.