A nine-year-old boy killed by a dog on a holiday park was alone in a caravan with the animal, police said.
Frankie Macritchie from Plymouth died at Tencreek Holiday Park, Looe, Cornwall, on Saturday.
The police said she was in the compound with adults, but they were in a different caravan when he was attacked by a "bulldog dog."
A person referred to by the police as a friendly family was later arrested at a train station near Plymouth.
The 28-year-old suspected of manslaughter has since been released.
Det Supt Mike West said that Frankie spent several evenings on vacation before his death.
"We believe that Frankie was alone with the dog in a caravan when he was attacked while the adults were on vacation with fellows in a neighboring unit," he said.
"These two groups of humans were known to each other and all from the Plymouth area."
The police were summoned to the holiday park on Saturday at 5:00 am BST and found Frankie "unresponsive".
He died at the scene and a search was started to track down the dog and its owner.
& # 39; Desperately Sad "
The 28-year-old woman, who was arrested for manslaughter, was also arrested on suspicion of being in danger of being out of control.
The dog was taken to Zwinger where he is.
Det Supt West said it was a "desperately sad event".
He said, "I also want to recognize those who came to his aid at the scene, civil servants and emergency services, who had to work in deeply disturbing circumstances."
"We are aware that this case is the one Public shock and anger. However, we urge the public not to blame it on this tragic incident and to allow ourselves to do our job and thoroughly investigate this matter.
Police ordered people not to speculate on what had happened on social media.