Sorry to hear about the tetra
How many fish do you have in this 15g tank? I believe you mentioned 2 mollys and 2 pearl gouramis.
Yes, this is normal behaviour, especially at feeding time. Although your fish (the two species you mentioned) are considered peaceful species, they can/will still display bullying at this time.
One way to maybe midigate some this behaviour (from my experience), is to feed your fish small portions twice or three times day. This allow fish that didn't get to eat at the first feeding another opportunity to eat and since they didn't get to eat the first time, they will more than likely be the first to go for food, at the second or third feeding. This is also, in my opinion, a more natural way to feed fish.
Hope this helps!