[Bicentric]

pawn Код:

stock IsPlayerKillingWithKnife(playerid)
{
    if(GetPlayerAnimationIndex(playerid) == KnifeKillAnim) return true;
    return false;
}

Replace 'KnifeKillAnim' with the animation ID. I don't know what ID it is for killing behind. I don't work with animations a lot, so I am not certain that it will work, but it compiles just fine if I put in a valid animation ID.