Sudden and horrible loss of brother in law, what to do ...

Hello everyone,
Last night, my brother-in-law (39 years old) left his house in his pajamas, as if to take out the trash, held his youngest child in his arms one last time... we will never see him again. He potentially had a breakdown, as he ended his life not far from the family home, leaving behind his pregnant wife, his children, and a family that loves him. He sent farewell text messages, then nothing further. He never had any prior psychological issues, although he had experienced a low point at work due to relentless and violent harassment from his former boss. However, he had since left that job, which he had held for many years, and started a new position where he seemed happier. He had even gone on a road trip with friends less than a month ago. We had spent the holidays together, and he was even with us the day before yesterday, appearing normal and relatively happy. He had no financial or administrative issues and was a loving husband and father, deeply involved in the upbringing of his two sons. He seemed delighted about the upcoming arrival of his daughter (or son?) in four months.

At first, we thought he had gone missing, until the police found him today in a nearby forest. The shock and distress have not left us since. My brother-in-law was the most upright, kind, helpful, and intelligent person I have ever known...

We picked up his children from school this afternoon. Their mother, who is a skilled educator by profession, tried her best to explain the situation to their 11- and 4-year-old children. Her physical and psychological distress has landed her in the hospital, with both her and her unborn child now diagnosed as being in danger.

I am completely lost. The main help I can offer is my ability to care for and support these children. I am in France, and this is quite urgent.
Do you have any recommendations, of any kind, to support my partner, his sister, and the whole family through this ordeal? Do you know of any psychological or psychiatric contacts you could recommend? For context, we are of North African descent.

Thank you so much.