Unfortunately that can do it, especially in a smaller tank.
Did you check you water parameters just in case?
Did you check you water parameters just in case?
Did you check you water parameters just in case?
Guess you'll just have to assume it was aggression. Just have to be careful with the next one. 
I just recently purchased a Yellow Lab female that is carrying from the LFS, She is still holding and is a lone in a tank to herself I will keep an eye on her to see if the samething happens which I am hopping it doesnt happen.
I talked to the man who I had left to take of the fry while I was gone, and he said they are all alive and well. I am going to pick them up sometime this week.
