Tiger Executions on the Canary Islands

Three tigers were shot dead by police and Civil Guards at the Canary Islands Zoo, located in Spain.The tigers had escaped from their cages when an employee had accidentally pressed the release button. While the total tiger count was 7, only 3 decided to leave their cage and venture out into the zoo. Thankfully, the Canary Island Zoo was closed for business at the time and the only employee on the grounds was the caretaker. Nearly 100 police ran to the scene and shot the tigers dead. Was this justified? Could these senseless deaths have been avoided? Could their lives have been spared if police attempted to round them up or used tranquilizer darts?