[veyron]

kills[MAX_PLAYERS]; // at top of your code

if(killerid!=INVALID_PLAYER_ID) kills[killerid]++; // OnPlayerDeath
new newtext[41]; // OnPlayerDeath
format(newtext, sizeof(newtext), "Kills: %d", kills[killerid]); // OnPlayerDeath
TextDrawSetString(killtext, newtext); // OnPlayerDeath

kills[playerid]=0; // on player disconnect, if player disconnects set kills to 0

timer isnt necessary, simply put everything under onplayerdeath