Three people were killed and dozens wounded in another violent weekend in Chicago .
21 people were injured in separate shootings between Saturday and early Sunday.
Among those killed was 28-year-old William Lewis. Lewis was in 1300 block of West Devon Avenue Saturday afternoon when a man walked up to him and started firing shots, police said. Lewis was hit in the back and died within an hour at St. Francis Hospital in Evanston.
The shooter fled the scene on foot, police said.