(1). Aiding, Abetting, Counselling and Procuring (Principal) (AACP)
(2). Joint Enterprise Liability
The doctrine of joint enterprise was distinct from the common law principles of accessorial liability whereby the person charged with aiding, abetting, counselling or procuring an offence could only be convicted if the principal offender, charged at the same trial, was found guilty of the relevant principal offence.( Sze Kwan Lung  3 HKLRD 328 (CFA))
First level Basic JE: if what happened is what they agreed to do, then it is straingtforward that JE is established and you should be liable.
Second level Extended JE: if what happened is beyond what they agreed to do, this does not mean that you should not be held liable. Should consider in two situations:
(a) First is if what happened within your contemplation and foresee, you will be still liable. (Chan Wing Siu v R.  A.C. 168 and approved by CFA in Sze Kwan Lung  3 HKLRD 328 (CFA), in UK, the The Chan Wing Siu principle is abolished in R v Jogee  2 WLR 861, but in HK, in HKSAR v Chan Kam Shing  HKCFA 87, CFA did not follow R v Jogee.).
It is irrelevant that Principal uses different weapon – provided D2 contemplates such harm might be inflicted. (Szeto Kwok-hei  2 HKLR 178). If the accessory knew that the principal had a weapon but the killing was caused by a different weapon of equal dangerousness, accessorial liability for the killing will arise.( R v. Powell; R v. English  1 AC 1 (HL)). D2 still liable if weapon used by P is different to ‗but as dangerous as‘ weapon D2 contemplate P might use. (R v. Rahman  UKHL 45).
(b) Second is if what happened is beyond your contemplation and cannot foreseeable, than you will not be held liable. (R v. English  1 AC 1 (HL))