Complex sentence: Young Brock Rumlow led the Savage Crims gang on New York's lower east sidehe assaulted fifteen year old Rachel Leighton, two of her brothers assaulted Brock, and the elder brother was killed.
Split into simpler sentences: Young Brock Rumlow led the Savage Crims gang on New York's lower east side. After he assaulted fifteen year old Rachel Leighton, two of her brothers assaulted Brock, and the elder brother was killed.