Thank you everyone. I was very upset about it last night, but I am just thankful I still have 2 corys left.
(Which happen to have fin rot -- I am treating with Melafix
Oh yes, and I'm not buying fish from Petsmart anymore.)
I am thinking about making a sticky to remind everyone to keep everything in their tank maintained, as the accident last night was completely my fault. The filter intake tube's screen had a hole in it, and the cory somehow managed to squeeze the whole and was killed by the fan. It was completely my fault. I had seen it before, but I didn't think anything of it. "Oh, nothing could swim through there," and look what happened. A tiny life was lost because of it!
Let this serve as a reminder for all of you. I had to learn the hard way.