Omen or Karma?

Sometimes it's hard to interpret random signs. Is it an omen? A test? A couple of days ago when I was walking my dog (not a euphemism for masturbation) I saw a cat pounce on a mouse and bite it to death as it was screaming. Is that a sign? If so, what does it mean? A month ago I was at a bar and I ordered a drink, payed for it with a $10 bill, but the bartender gave me change for $20. Since