I get all that, but he had a choice to simply walk away. He decided to undergo a difficult process instead for which I laud him. But not everyone is made to handle and take the blowback. He could have simply collected the material, looked for a new job, gotten the new job offer and then left the firm and handed over the material to regulators. If he did not trust the regulators would act on the material he could have publicized the issue with a new secure job in hand. Many different options. He handled it quite poorly if you ask me. Nobody said the process of blowing the whistle is easy. Respect to him again. But he also had a choice to confide in his fiance for support instead of running away (and he literally dumped her in the worst possible way and kept a secret from all his trusted loved ones), he chose to escape into alcohol and sleeping pills. Lots of choices and he picked all the wrong ones in that regards.
My perception, this person was looking forward to a new job, looking forward to marriage and being part of a happy team where he was accepted. The last thing he was expecting was confrontation and excommunication, being shunned. Not only that but he was highly disgusted with the blatant unethical behaviour of the company, that must have sent a chill through his body - who wants to be found guilty of misconduct due to being tarred with the same brush?
Then there was the added workload of ferreting out proof and colating it for HR.
All of a sudden his world collapsed, what was originally a dream job turned into a nightmare.
I can understand the fear, he wanted a job and to being paid, but not with a gang of supposed crooks.