Shazimyr Frost is a hard man to read. He can be quite unlikable when you first meet him. His posh attitude and apparent lack of empathy toward others comes off very strongly when you first meet him. Despite this, he is very loyal to his few friends and people that earn his respect and is very empathetic toward those who he deems worthy of his esteem. He has a dark sense of humor and is very witty. He has a century-old Mid Atlantic accent that makes you wonder if he time traveled from the year 1920.
If you were to ask him what he did for a living before the outbreak, he'll tell you he was "merely a real estate investor" or something of the sort. Those that were close to him were very aware of his shady dealings in the underworld, including but not restricted to: drug manufacturing & distribution, illegal gambling, and probable affiliation with organized crime in both the US and UK. Although he could very well have been a criminal mastermind, his overly charismatic attitude can sometimes be so ridiculous to the point where no one takes him seriously, which he is able to use to his advantage in certain situations.
Mr. Frost was aboard a cruise ship that struck a rock formation and sunk as a result of a massive storm, and was able to board a lifeboat that travelled north and ended up on the shores of Chernarus. He had heard news of the wars and outbreak weeks before on the cruise ship, but had little to no idea of what awaited him in this freshly post-apocalyptic world. With no form of communication with the rest of the world and very few other survivors, Shazimyr's primal instincts kicked in and he knew he would have to use every bit of resourcefulness and cunning he had within him to survive and find a way out... using whatever or whomever he has to in the process.
After a couple months in Chernarus, Shazimyr has adapted quite well to the harsh realities and survival techniques of a post-apocalyptic world. Foraging and hunting are a second nature, and manipulation of other survivors has become a necessity. Dispatching the infected has evolved from a daunting task into a boring chore for him, after finding that he is one of the very few immune to the infection. He has interacted with so few intellectual human beings that he may be slowly spiraling into insanity. Perhaps the preservation of humanity is necessary if not for the greater good of mankind, then at least for the greater good of the sanity that he has left.