In this scene, Both Scout, Jem, and Dill all show fear of Scout ending up right in front of the Radley house when Jem rolls her down the street.
Get away from those kids!
In this scene Scout and Dill were very afraid for Jem because of what they saw which later Jem sees while trying to look in the back part of the Radley house. They were in fear because a looming dark figure going back and fourth across the porch towards Jem.
In this scene Scout is terrified and in fear of what the old Saram group would do to Atticus in order to get in the Jail and get Tom Robinson.
In this scene Scout and some part of Jem were in fear for their lives while Bob Ewell attacked them having the intent to try and hurt them, but Arthur/Boo Radley came to help them and ending up stabbing Bob under the rib cage and carried Jem back home setting him down in his bed.
Tom Robinson is a "Mockingbird" because he was "killed" and physically killed because he was framed by the Ewells for raping Mayella Ewell but it actually the other way around because Mayella asked for his help and held him down trying to kiss him. And he was physically killed trying to escape jail because he knew he was innocent.
Arthur (Boo) Radley was a mockingbird because he would help Scout, Jem, and sometimes Dill when they were in trouble, like sewing Jem's pants when he teared them, he helped Jem and scout from Bob Ewell and ended up killing Bob. He cares about the kids and tries to help when they need it the most.