On December 31st, 1941, Soviet troops temporarily liberated Kerch and excavated mass graves filled with Jewish victims of the Nazis. These were photographed by photo-journalists who included Dmitrii Baltermants, whose photos were published in Ogonyok on March 2nd, 1942. David Shneer gives an account of the photographs here and provenance is also discussed here. Finally, the excavation was witnessed by Jewish-Russian poet Ilya Selvinsky, who recorded it in his diary and in the poem "I Saw It!", which was published in a Soviet newspaper on January 23rd, 1942; extracts from both sources are translated and discussed by Maxim D. Shrayer here. These sources deserve wider exposure and attention.
NOTE: Jason Myers kindly reminds me that the commander recorded the massacre thus: "Die Umsiedlung der Juden, etwa 2500 an der Zahl, wurde am 1., 2. and 3. Dezember vollzogen. Mit nachtraeglichen Exekutierungen ist zu rechnen, da ein Teil der judischen Bevoelkerung fluechtete, sich versteckt haelt und erst aufgegriffen werden muss." [Dok. 126 in this collection]. Umsiedlung replaced a crossed-out word, which may be Liquidierung or Exekutierung; see footnotes 5 and 6 in the link.