Conversation so far:
What kind of controversy surrounded Chong regarding his legal issue?
There was a controversy about the disparity in sentences between Chong's and those of other defendants and the DEA tactics used in the investigation.
What was the DEA's investigation regarding Tommy Chong?
Federal agents investigated Nice Dreams, the headshop owned by Tommy and Prince Chong.

Question: What did they do while inside the shop?
Self-contained rewrite: What did the DEA do while inside the shop Nice Dreams?