It isn't retail investors. Clearly being manipulated by a large trader selling a huge number of small lots into the market instead of a large block trade. Selling pressure started in pre-market the moment earnings numbers were released (before anyone had time to actually read the data, which isn't really that bad and certainly not 8% haircut bad).
Compare the options activity yesterday and today. A lot of $40 calls sold to collect a premium, selling pressure to drive the stock down, write $35 puts today to collect another premium, buy back the calls to close. Who has $42M cash in their pocket to cover the sale of 12,000 put contracts?
KR will be range bound between $36 and $41 for a while.