Police believe poachers may be behind upsetting incident.
The llama, called Larry, was shot and killed at the Hilltop Farm Animal Sanctuary near the village of Longhorsley, Northumberland, last week.
It is believed those responsible had entered the farm overnight on Wednesday and Thursday before shooting the animal and fleeing the area.
Larry's body was then discovered the next morning in the field that the animal shared with a flock of alpacas.
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Police have been informed and are carrying out an investigation to try and identify the suspected poachers responsible for the killing.
And now officers have warned those who carry out illegal hunts in that they will be arrested if they are identified.
Sergeant Mick Aspey, of Northumbria Police, said: "This heartless shooting has understandably led to outrage in the community and on social media.
"Larry had been at the sanctuary for five years and was a loving, harmless animal that has been gunned down by suspected poachers.
"It has been reported to us that those responsible may have mistaken Larry for a deer but even so it is illegal to hunt animals in this way.
"We know that poaching can be a problem in our rural communities and I want to reassure people that we take it seriously.
"It is a criminal offence and, where possible, we will always look to identify offenders and put them before the courts.
"Enquiries into this incident are ongoing and I would ask anyone who saw anyone acting suspiciously in the area of the sanctuary to get in touch."
It is believed the attackers would have accessed the farm, on the A697 near Espley from the back, on Beacon Hill.
Anyone who has information that may assist police should contact officers on 101 quoting log 915 26/02/19 or report it online at our website.