How was Harry going to kill Sirius?

[Jim Ferer]

No: HPFGUIDX 53207

Maggie:"Back to the Shrieking Shack.  How did Harry intend to kill
Sirius?  He didn't yet know of Avada Kadavra, or, as far as I know,
any other way of magically committing murder.  Is there something I'm
missing?"

We see more than once that a wizard feels threatened if he has a wand
on him, even from someone who's really unlikely to know AK. 

There's one possibility that's occurred to me. If you recall from GoF,
in the graveyard, Harry is running away from the DE's, who are trying
to stun him.  Harry dodges the spells, and *he hears gravestones
cracking and being broken.*  Also, James and Lily's house is destroyed
when Voldemort's AK fails. Why? How?

Apparently a spell has some physical force to it, especially when it's
misdirected.  It may be that Harry was going to give Sirius a
magically generated punch hard enough to kill him (If you recieve a
hard enough blow right in the chest, it can kill you; it happens all
the time in auto wrecks without airbags). I don't think a thirteen
year old would think he could kill a madman with his bare hands,
emaciated or no.

AK simply takes away the life spark without leaving any other trace,
but that leaves the door open to more mundane ways of doing someone in.

Jim Ferer