Spanish police were acting on a European arrest warrant requested by Hampshire Constabulary when they arrested the Kings.
When they stopped the family's Hyundai people carrier officers found Ashya and his parents inside.
Mr Shead said: "There are no winners in this situation. I've said all along that this must be a terribly distressing time for Ashya's family and I stand by that now."
He added that it was too soon to say when Ashya would come back to the UK but Southampton General Hospital have been contacted so they can liaise with the medical taking care of him in Spain.
"Ashya's brothers and sisters were not in the vehicle," Mr Shead said. "We have located them. They're all okay, they're fine. They are actually in a hotel about 10 miles away."
He also said that a team of Hampshire police officers would be going to Spain tomorrow to continue the investigation.
Meanwhile, in a video blog posted on YouTube by Ashya's brother Naveed, their father, a Jehovah's Witness, said Ashya was doing well and explained that the family had decided to take him out of hospital to seek a cancer treatment not available on the NHS.
Sitting on a bed with Ashya in his arms, Mr King said: ''We were most disturbed today to find that his face is all over the internet and newspapers and we have been labelled as kidnappers putting his life at risk, neglect.''
Mr King said there had been ''a lot of talk'' about the machine used to feed Ashya and whether they could make it work.
Police had warned that the family might not be able to work the machine and that it would run out of battery power.