New guy at my job, polish dude. He seemed decent enough, just a bit.... odd... but most of us were; after all, we were the kind of people who are willing to work on ships on the wrong side of the world for weeks, sometimes months at a time.
I trained him to do the job I did, so he could run opposite of my shift, with some assistance from the chief tech and various others. The rest of the crew were pretty experienced, so it made it easier when he needed help with the more complex stuff. He did reasonably OK for a newhire. Nothing spectacularly good, but nothing spectacularly bad either.
Until the crewing department told us he had been arrested back home, multiple counts of murder, and we were unlikely to have him onboard again, so we needed to train his replacement.
Turned out he was a serial killer who killed people for their properties. He's in prison now, and I'm sure you can google the person. I'm not sure what his actual name was, but we called him Winny. Any poles here who happen to remember the case and could link a news article? This happened roughly 10 years ago.