Drills like this are standard procedure at many zoos (at some U.S. zoos that are certified by the Association of Zoos and Aquaria, all the employees carry out various drills for animal escapes or disaster situations several times each year) -- though never has the "escaped animal" actually been shot.
The bizarre story -- almost too strange to believe -- is yet another testament to the lack of safety precautions at parks like this.
Even worse, this isn't the first time that Loro Parque has been the site of a horrific accident involving a park employee. On Christmas Eve of 2009, an orca whale named Keto (who was born at SeaWorld Orlando) attacked and killed a trainer, 29-year old Alex Martinez, during a training session. The event became a rallying call for many opponents of orca captivity, who say that the practice is dangerous both for people and for animals.
Update: Loro Parque issued this statement to The Dodo:
After the appropriate emergency mechanisms for this type of situation were activated, one of the animal keepers of the terrestrial mammals was accidentally hit by a tranquillizer dart which the veterinarians have to have ready for such cases. Because of this he was rapidly assisted by the Emergency Medical Service and immediately transferred to the University Hospital of Tenerife where he was attended to and subsequently discharged. The employee has fully recovered and was released from the Hospital this morning and he would like to thank everyone for all the displays of concern and affection that he has received.