His attacker

approached with his right palm turned into his right thigh so
that his knife was hidden. He got very close to my friend and
asked a question to distract him, then he plunged the hidden
knife into his heart. That single stab wound killed him. So
look out for concealment, if you can't see the attacker's hands
or if his palm is turned in or even if the attacker has his hand
in his pocket, you have to ask yourself why. It is very likely
that he is concealing a weapon. Cannan used to carry an old
carrier bag in which he kept a number of dangerous
weapons. When he asked his intended victim a question,
again as a distraction, he would reach into his bag and take
out his implement.
If the approach is made by more than one person they will
all usually display the same physical traits.