

4000 were deported back to Germany, where they ended up in concentration camps
Counts as a “had them killed,”
Yes, likely to a large share. Stalin sent those members of the KPD to (almost) certain death, who weren’t completely in line with the Stalinist ideology. If they belonged to the party elite, there were rightoff killed by the NKVD directly.
Definitely. If I get the German and English Wikipedia articles right, it was the remaining inner circle of the KPD (Pieck, Ulbricht, Mielke) denouncing the others to the NKVD.