The dog's owner and her young daughter - who was the dog's "best friend" - had to jump in a lake to escape.
The mother and daughter suffered minor injuries but their one-year-old dog Larry died at the scene.
Nottinghamshire Police seized four dogs and is investigating the attack at Vicar Water Country Park, Clipstone, on Wednesday morning.
Larry's family said in a statement: "We are heartbroken over what has happened.
"Larry was loved and cherished by all who met him, especially our three-year-old daughter who referred to him as her best friend."
Police were called to the park at about 11:00 BST on Wednesday and the 23-year-old mother was taken to hospital.
The four dogs were seized under the Dangerous Dogs Act, and police said they would be "kept in a safe and secure environment whilst the investigation is conducted".
If the dogs are considered to be dangerous, an order for their destruction could be made. The dogs' owner or owners could also be prosecuted.
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