The veterinary profession has the highest suicide rate of all professions – some reports say  it is four times higher than the general population and twice as high as doctors and dentists. The causes we are able to identify stem from an overidentification with animals in pain, fatigue, irregular hours, overwhelming workloads, the expectations and demands of clients, working in an environment of psychological or physical isolation and lack of tools or resources to deal with stress.
All other professions have a direct relationship with the recipient of their services.  The veterinary profession is unique in that it deals with a third party – being the owner of the animal – and not the patient directly.  The owner often doesn’t understand the medicine or surgical techniques required for treatment, or the consequences of taking certain steps in the treatment, yet the owner makes the decisions. The owner has complete control over the patient and there is often major conflict between the patient’s needs and the owner’s wants.
The patient cannot talk to the veterinarian so diagnosis often requires laborious testing and approaches to treatment that do not always work first time around.
Money is always an issue.  Veterinarians rarely, if ever, are able to perform a thorough and complete diagnostic work up, due to the owner’s financial constraints.  Yet owners often have “human medicine” expectations.  
Medicine is hard for lay people to understand and people are frequently emotional and irrational where animals are concerned and unable to be objective.
All these factors can work together to create the perfect storm in certain clients.  The mix of misunderstanding, emotions, and irrational thoughts lead some people to feel they must take revenge for whatever reason.  This often happens under the misperception that the client should act as advocate to stop the veterinarian from “harming” more animals. This emotional approach leads many people to bring the situation to a public platform, creating intense pressure on the hapless veterinarians involved.
Veterinarians under stress for all of the above-named reasons will sometimes have suicidal thoughts and have been known to follow through, thinking that this is the only way out.