We cannot say for certain whether Hitler had decided by early October 1941 to exterminate Europe's Jews in death camps. We can be sure, however, that Heydrich wished to exterminate them on German-controlled soil. Here's how. On October 2, 1941, Heydrich ruled out the resettlement to the East of Czechs who were hostile to Germany because "they would form a leadership class in the East, which would be directed against us [denn aussiedeln kann ich sie nicht, weil sie drüben im Osten eine Führerschicht bilden würden, die sich gegen uns richtet]." He stated that these people should be "put up against the wall [sie endgültig an die Wand zu stellen]." However, two days later, Heydrich met Meyer, Leibbrandt, Schlotterer and Ehlich and moaned that demands for Jewish labour would prevent a "total resettlement of the Jews out of the territories occupied by us [NO-1020, in VEJ 7, p.153: "Dies würde aber den Plan einer totalen Aussiedlung der Juden aus den von uns besetzten Gebieten zunichte machen]."
These statements can only be reconciled if Heydrich's "totalen Aussiedlung der Juden aus den von uns besetzten Gebieten zunichte machen" is a euphemism for killing the Jews within the territories occupied by the Germans, because the statement of two days earlier had ruled out the resettlement of hostile populations in colonies in the East, and Jews were intrinsically a hostile population in the Nazi worldview, as shown by Heydrich's statement at Wannsee that any remnant of Jewry had to be "treated accordingly, because it is the product of natural selection and
would, if released, act as a the seed of a new Jewish revival (see the
experience of history)." This is also confirmed by the fact that Heydrich blocked the emigration of Spanish Jews residing in France
to Spanish Morocco because, in Heydrich's words, "these Jews would also
be too much out of the direct reach of the
measures for a basic solution to the Jewish question to be enacted after
the war [see Browning's footnote 17 here]." Heydrich's plan was therefore clear; the only question is whether or not Hitler shared it by that date; and if not, how long did it take for Hitler to give the green light?