PoA: How would Harry kill Black?

[Krolik]

No: HPFGUIDX 30206

I checked the FAQ and apparently this has not been discussed before. I 
am sorry if it has. 

In PoA, Harry aims his wand at Black with the intention of killing 
him. How exactly does he think he will do it? We get the impression in 
GoF that Harry does not know about Avada Kedavra at this point. Does 
Hermione know? If so, she would also know that using a curse to kill 
somebody, for whatever reason (is that right?) will land you in 
Azkaban for life. Why does not she stop Harry? It appears that both 
Ron and Hermione do not try to stop Harry because they believe it is 
his right to do with Black what he wants (although they hope he will 
decide against murder), but it would be very un-Hermioneish not to 
warn Harry of the possible consequences.

Krolik