It would be like killing a mockingbird and mockingbirds do not harm anyone or disturb anyone. Boo never disturbed anyone or harmed anybody. If people knew Boo was the one who killed Bob Ewell, then Boo would've got all these attentions and he does not like attentions.
Heck Tate wants to protect Boo Radley, who killed Bob Ewell, because he believes Boo acted in self-defense to save Scout and Jem. Tate wants to avoid the publicity and attention that would come with Boo being hailed as a hero, recognizing that Boo would not want the attention.
Boo Radley killed Bob Ewell because Bob was trying to kill Jem and Scout. At first, Atticus believes Jem did it. Heck Tate insists that they claim Bob Ewell fell on his knife. Atticus thinks Heck is protecting Jem and he does not want to cover up what he thinks happened. When he finally understands that Boo did it he agrees to the lie.
In "To Kill a Mockingbird," Heck Tate finds Bob Ewell dead in the woods after Boo Radley intervenes and saves Scout and Jem from being attacked by him. Heck Tate initially tries to cover up Boo Radley's role in the incident to protect him from unwanted attention.
Heck Tate is covering up the truth about Bob Ewell's death to protect Boo Radley, who actually killed Bob in defense of Scout and Jem. Tate believes that revealing Boo's involvement would subject him to unwanted attention and potentially harm his reclusive lifestyle.
Boo Radley risked his life and rep (therefore sacrificing) to save the children. Heck Tate...he didn't sacrifice much.
Heck Tate insisted that Bob Ewell fell on his own knife to protect Boo Radley, who had killed Ewell in order to save Scout and Jem from being harmed. Tate believed that exposing Boo's actions would bring unwanted attention and possible harm to Boo, so he chose to keep the truth hidden.
Heck Tate insists that Bob Ewell's death was self-inflicted because he wanted to save Boo Radley (who actually killed Bob Ewell) from the spotlight that would come from everyone finding out that Boo killed Bob.
Boo Radley
Boo because jem was knocked out
Heck Tate claims that it would be a sin to expose Boo Radley to the attention and publicity of the town after Boo saves Scout and Jem from Bob Ewell. He believes that Boo deserves to remain private and out of the public eye.
Heck Tate decides that Bob Ewell fell on his own knife because he wants to protect Boo Radley, who actually killed Bob Ewell to save Scout and Jem. Tate believes that revealing Boo as the hero would subject him to unwanted attention and publicity, so he opts to keep the truth hidden for Boo's sake.
Boo because jem was knocked out