Motive is the plausible reason the suspects murdered three people. The best way to understand this is to look at what happened at the time of the murders:
- identification/wallets stolen
- vehicle stolen
Murder during robbery is so common it's clearly defined in law. I'm very confused why so many want to look around the obvious and proclaim that murders, where property was stolen, are a mystery.
"Culpable homicide is murder where a person causes the
death of a human being while committing or attempting to commit ... an offence mentioned in section 343 (
robbery), whether or not the person means to cause death to any human being and whether or not he knows that death is likely to be caused to any human being, if
(a) he means to
cause bodily harm for the purpose of
(i) facilitating the commission of the offence, or
(ii) facilitating his flight after committing or attempting to commit the offence,"
Criminal Code