Toward the end of chapter 28, Scout describes Bob Ewell's attack and attempts to identify the person who saved her life. When Scout mentions that a man came to their aid during the fight, Sheriff Tate asks Scout the man's name. Scout does not know the man's name but points toward him and says,
Why there he is, Mr. Tate, he can tell you his name (Lee, 274).
Scout proceeds to point toward Boo Radley, who is silently standing in the corner of the room. After examining the man's pale skin and hollow cheeks, Scout recognizes the person who saved her life by saying, "Hey, Boo" (Lee, 274).
In chapter 30, Sheriff Tate and Atticus are discussing the person responsible for Bob Ewell's death, and Sheriff Tate indirectly tells Atticus that Boo Radley killed Bob Ewell. Sheriff Tate tells Atticus,
To my way of thinkin’, Mr. Finch, taking the one man who’s done you and this town a great service an‘ draggin’ him with his shy ways into the limelight—to me, that’s a sin. It’s a sin and I’m not about to have it on my head. If it was any other man, it’d be different. But not this man, Mr. Finch (Lee, 280).
Sheriff Tate understands that informing the community will harm Boo, who is extremely reclusive and would not enjoy the excessive attention, which is why he does not publicly announce Boo's heroics.