A feral dog ran at another dog and its owner in Apsley Lock last month, knocking him to the ground.
Hertfordshire Constabulary are appealing for witnesses who saw the incident take place to come forward.
On Monday, July 22, at around 1pm, a dog described as a black and white Japanese Akita charged at the owner and their dog in Apsley Lock, knocking over the owner and biting the dog on the leg.
Although no injuries have been reported to police, they are asking for people who may know the dog, and its owner, to come forward.
If you have any further information regarding this black and white Japanese Akita please contact 101 using the crime reference 41/68218/19.