Why would a seagull go after an eagle?

I witnessed a number of seagulls making a very loud noise or crys if you like to describe it that way ,over a rooftop.within a short period of time the number increased and the noise became greater.

I kept my eyes focusing on the roof top ,suddenly one of the seagulls picked a dead chick and dropped it on the side ,and did the same again to another dead chick. After this bazaar behaviour noise got lower and lower and the number of the seagulls gathering became smaller .

The only explanation to such behaviour is either it was a killing of the occupants of the nest or a cry of sorrow to a loss of the chicks to conclude the answer ,i think it was a killing of other sea gull's chicks wher the mother was over powered by a male seagull and somehow the male wanted to show other seagulls his strength and to encourage the females to mate with him.