Nobody is surprised by this.

He shouldn't be allowed to operate aircraft in the meantime

https://www.caa.govt.nz/assets/legacy/medical/Med_Info_Sheets/MIS016.pdf

Why is depression an aviation safety problem?

Impaired or poor decision-making. Depressed people think more slowly and less efficiently than others. This can result in slow and poor decision making, which is not a desirable situation for aviation safety.

Poor judgment. People who are depressed do not always exercise sound judgement, another feature that is not desirable for safe aviation.

Lack of insight. A lack of insight, including insight into the severity of their condition, can be associated with a variety of medical conditions including depression. Insight, into your own health situation as well as the requirements for aviation, is essential for safe aviation.

Associated disordered behaviour. Sometimes depression is associated with bizarre and dangerous behaviour. This can range from angry outbursts through to paradoxical great elation and manic hyper activity or even hallucinations. Such behaviour is clearly not compatible with safe aviation.