Two dogs were burnt alive when arsonists set fire to a car parked at a boot sale.
Firefighters were unable to save the animals trapped in the burning Vauxhall Cavalier in Whitchurch, Bristol, when the alarm was raised.
The owner of the vehicle, believed to have been shopping at the sale, was said to be "distraught" after returning to her car and finding her pets had been killed shortly after midday on Saturday.
Inspector Phil Robbins of Avon and Somerset Police said said: "It is unlikely anyone could not have noticed the dog and small puppy inside the car.
"The fire was started intentionally and we are investigating.
"The owner of the vehicle was distraught and needed medical attention."
The Vauxhall had been parked in the visitors' area of an airfield near Whitchurch Sports centre.
A fire service spokesman said: "The female owner was treated for shock, The fire was started deliberately."
