Conversation so far:
When was Erich Mielke imprisoned?
On 7 December 1989, Erich Mielke was arrested and placed in solitary confinement.
What crime was Erich Mielke convicted of?
After twenty months of one-and-a-half hour daily sessions, Erich Mielke was convicted on two counts of murder and one of attempted murder.
How long was Erich Mielke imprisoned in total?
Erich Mielke was incarcerated for 1,904 days.

Question: What happened during his imprisonment?
Self-contained rewrite: What happened during Erich Mielke's imprisonment?