CHICAGO (CBS) — A 24-year-old man was killed and a 23-year-old man was grazed by a bullet in a shooting in the West Lawn neighborhood late Wednesday night, capping off the most violent month in Chicago in 20 years.

Chicago police said there were 90 homicides in August, and a total of 472 people shot in 384 separate attacks. The city has not had that many murders in one month since August 1996.

As he has several times before, Police Supt. Eddie Johnson said a relatively small group of repeat gun criminals are responsible for the the vast majority of gun violence in Chicago. The department maintains a watchlist of sorts, called the “strategic subject list,” which relies on an algorithm to try to predict who is most likely to be involved in a shooting – either as the shooter or victim – by analyzing data such as gang affiliations, criminal records, past shootings, and previous contact with police.