A youth who snatched a white rabbit at a zoo and threw it into the alligator pool is being sought by police.
Albert is 4m long, thought to be the largest aligator in the UK
Customers at the Welsh Mountain Zoo in Colwyn Bay were horrified to see the tame animal still alive in the reptile's jaws before it was killed.
Zoo director Chris Jackson said staff and visitors were "sickened" by the "senseless barbarity" of the rabbit's death.
Staff detained one youth and handed him over to police, but two more got away.
The zoo has two Mississippi alligators, Albert and Nancy, both more than 30 years old and the only breeding pair of the species in Europe.
He said the youths were thought to have climbed over a wall into the zoo, which occupies 37 acres of woodland and parkland.
He said: "They looked at the alligators, then went into the children's farm and looked at the rabbits.
"One of them decided that it was his sick agenda to take the rabbit. It was in a petting area, where the small children are encouraged to get close to them.
"He grabbed the rabbit and took it a distance of 20-30 yards to the alligator beach and threw it into the pool."
A visitor with his young daughter raised the alarm.
"These youths drew attention to themselves with their remarks, which made the man and his daughter look to the pool and they saw the rabbit was in the jaws of the alligator," said Mr Jackson.
The zoo's alligator pool has an artificial "beach" with outdoor sun lamps under which the alligators can bask. It is surrounded by a 4ft (1.2m) fence. The rabbit was grabbed by the male alligator, Albert.
The alligator, who has been at the zoo for more than 20 years, is in excess of 4m long is believed to be the largest alligator in the UK.
Mr Jackson said: "The alligator quickly took the rabbit underwater. While one worries about the terror and the fear of the rabbit, its suffering would have been relatively limited."
He said Albert reacted like any alligator with live prey, drowning it first and eating it later.
In the wild, alligators feed on a variety of small animals including fish, birds and mammals.
In the zoo, Albert and Nancy feed on fish and meat, usually herring and beef.
Security at the zoo is being reviewed. The site is run by Mr Jackson and his brother, Nick, and was opened by their father in 1963.
North Wales Police said no-one had been charged but they were following some positive lines of inquiry.
Mr Jackson said: "We're disgusted, speechless and shocked. If you spend your life working with and looking after animals, this is something you cannot conceive."