First I do some background checking to see which one would be the best one to choose first. I make acquaintance, have a couple beers with him/her, talk about this and that. During the next couple of weeks I proceed to befriend him, take part of his hobbies and continue to spend time with him. Now I've gained his trust, so I carefully lure him into a pyramid scam, that I've began a couple years before, with actually making an honest business with a clear record.
There's no chance of him not taking the bait. I also make sure that he thinks I'm not in any part of the pyramid scam as he has only dealt with a buddy of mine, who's actually me in a disguise. During the next few months all his invested money is gone, half of it come back as profits for him and then I've made him invest every last bit of money he could get anywhere. Now he's broke.
I've kept friends with him all along and his spirits have gone quite down with being broke, and the stress from it has snowballed into his others relationships getting worse, and all the people he has loaned money from don't think too highly of him anymore either. As he seeks help from me to his awful situation, I slightly put him down even more. At this point I've planted seeds of clear evidence of his wife cheating on him. As he begins to realize his wife being dishonest, I send a letter to her, which he'll read first with his raised suspicions. The letter makes him believe the affair had been going on for years.
I've sent the wife on a week long surprise holiday with the kids with the money I've got from the guard with the scam. I assure them I'll tell her husband and he'll join them later. At this point, as the only person he could trust, I've made him at least depressed and also an alcoholic or a drug fiend. Now I lie him, while he's intoxicated but with full of thought, that his wife has left him and taken the children with her because he had beaten and mistreated them. He can't remember it, but I ask him what he did the day before and he can't remember any of it, because I had drugged him unconscious for that day.
I confuse and depress him even more and suddenly break relations with him. While I'm leaving, I tell him that the neighborhood is furious with him, hearing rumors about him beating his family, doing hard drugs in front of his children etc. I leave his house and visit the neighbors telling terrible things about him. Even the breaking of windows around the neighborhood for the last week, is now an act that everyone's convinced of the guard being the culprit. After I took my last leave of his place, I had confiscated all his alcohol and drugs, but left a loaded gun in the house. There are also a dozen of tiny concealed audio players, full of recorded loud cries of help, around the house, with timers that set of simultaneously. The only movie he has, is Shawshank's Redemption, which he hasn't watched before. I've also edited it so that it ends the halfway through, on it's most saddest point. Now we've got everything set in the house, with the loaded gun as the cherry on the top. I also destroyed the lock on the main door so it can't be opened normally. Then there are the people from the neighborhood who are furious and will form an angry mob to crush his house and attack him.
That ought to do the trick. Then to the next guard...