Hmmm, yes ... I now see what you mean.
Closing price $68.84 at 16h00 EST.
In total, under 2500 shares of DUG were traded between 16h00 - 20h00 EST, most at prices nearish to the closing price ($68.84).
But 660 shares (i.e. about 25% of the volume traded in the after market session) were traded at $73.93 at 17h31 EST...
Am guessing somebody got stuck with a 660 share short position that they didn't cover during market hours (internet service down in Papua New Guinea, broker software not working, medical emergency, new addition to the family, fell asleep, etc ... ?).
After hours they got taken advantage of when liquidity dried up ... ?