Einsatzgruppen
Many other papers and reports written by the Einsatzgruppen talk about how many people the different units killed.  For example, one researcher looked at over 200 Operational Situation Reports (reports from the Einsatzgruppen to their bosses about what they were doing).  He also looked at letters and reports written by Einsatzgruppen bosses.  He found that as of 1942, Einsatzgruppen A, B, C, and D had killed almost a million people: