Complex sentence: In 1987 crack exploded in the city, as did territorial wars among drug dealers; 1988 saw 369 homicides in DC, shattering records that were broken again with 434 homicides in 1989 and 474 in 1990, making Washington's murder rate the highest in the nation.
Split into simpler sentences: In 1987 crack exploded in the city, as did territorial wars among drug dealers; 1988 saw 369 homicides in DC, the most ever in the city. That record was broken again when the next year had 434 homicides, and it was broken yet again when 1990 had 474 homicides, making Washington's murder rate the highest in the nation.