I think all the criteria should be addressed. Also, I think further requirements come to light
a. The person and Asmo are recognizable to eachother. Asmo's "You?" is clear. The speed of the killer's action indicates he/she knew Asmo's face because Asmo was not expected.

b. why didnt asmo see the person before he stepped thru the door/what's with this delay?
1. Asmo didnt expect to see anyone so not really looking. his guard was down.
2. the culprit was hidden somehow --naturally, chanelling or by object of the power. Had reason to hide other than ambush Asmo.
3. Asmo arrived there first. how would they get there?
4. Asmo teleported. to where? how? why?

c. Is there meaning to the way the "You?" came off as surprised?
1. Recognized the person but didnt expect him/her there.
2. Recognition of the person was based upon what they were doing.--Asmo's knowledge of someone whom he hadnt met.

d. Is there significance to the quick "No!"? Recognition is juxtaposed with understanding.

1. The killer is a person that Asmo knew would kill him immediately.

e. Is the sound of the words after death important? They hang in the air after death took him.
1. May rule out balefire b/c he died b/f he said the word. was this a RJ hint to rule out BF?
2. May rule out mundane means b/c there is no other sound made when he dies. not even an "ouch". Is the sound description an RJ hint b/c he is describing what you hear and is describing the sounds made by Asmo when he dies. How plausible is it that Asmo was stuck with a sword or such and simply continued with the Nooooooooooooooooooooooooooooooooooo during and after death.