Dead and dying children at work
I was hired as a Business Consultant at a firm in the Netherlands, and then demoted to SysAdmin because my Scottish accent was too strong. I wasn't happy at that, and I never wanted to be the PC police especially in a country where laws and attitudes towards sex were so different.
Engineers and salesmen would dial in to use the (then) high speed and free office internet rather than take out an account of their own. Even the ones with their own internet connections would view porn via the office presumably as they assumed it gave them more plausible deniability. The company internet server cache was massive, and at least three quarters of it was porn, as I found out when I had to investigate exorbitant charges from our ISP. It was hard to look at any of my co-workers the same way, especially the women. I sent out a memo to everyone explaining what a cache is, and asking them not to view anything they wouldn't want me to have to view, and instantly the internet bill was halved (and nobody could look at me either).
I've had a few experiences of being surprised or shocked by porn at work, but nothing close to "call the police", maybe I'm just deviant. I worked for an imaging/workflow company once, and they were trying to prove their system to a local NHS, so I was made to scan in and process sample medical records they provided, perhaps illegally. That was the most traumatic two days I ever spent at work. All the records were dead and dying children: X rays, photos, case-notes, etc. When you lot talk about things you can't unsee, well nothing I saw hadn't already been seen by a dozen doctors and nurses who probably see that sort of thing every week. They have all my respect, because decades later just thinking about it has me crying and reaching for the brandy.
I was asked to fix a Belgian guys laptop once, it was running slow. AVG identified over 37,000 viruses on it. That was unusually high so I went to delete the internet cache, and it had already been deleted but all the sites were still there - IP numbers rather than URLs, all Russian. He'd been engaged to a local woman who privately accused him of being a paedophile, and I'd seen him groom, kiss and even lick her daughter, I was certain she was correct. I didn't have enough evidence against him to phone the police, but I kept tabs on him. He later joined a social group where he had access to their children as a figure of trust, so I warned them about him. He had me charged by the police for doing that. They dropped my prosecution when I mentioned I had a recording of his ex-fiancee discussing his behaviour.
On a US magazine website I recently had my first conversation with someone who admitted to being a reformed paedophile, which I found very interesting. I'm a hang'em and flog'em guy when it comes to adult abusers, so it was informative finally being able to "Ask me anything". I think I have a better understanding of it now but I'd still recommend that if you can take action against someone who is a child-abuser, or even against someone who gets off on images or video of child-abuse, then you should do what you can. According to the honest paedophile I talked to, one thing does lead to another worse thing.