In a typical viking voyage the vikings attacked people and robbed as much of their belongings as they could. Of course they took part in several fights. Then the vikings came back with lots of stolen property and thus became very rich.
When Egill and Thorolfur went to Kurland at first their voyage was very successful, i.e. they killed and robbed without being disturbed. But then some natives arrested Egill and 12 of his men. By luck and Egill's skill the vikings managed to get away from the farm where they were held prisoned, before the natives killed them But Egill didn't want just to run away so he went back (he said that the natives should know about their escape and that they had stolen the farmer's weapons and silver) and killed everybody on the farm. He put the house on fire, waited outside and killed all those who managed to get out of the burning house. The others were burnt alive inside the house.
This way of living has probably suited Egill perfectly because he was very bad-tempered and full of violence. He also was a berserk, as his father and his grandfather.