Common foul committed during free throws?

[Carlos2283]

The rules book seems to mostly cover lane violations scenarios by either A or B but what about a foul committed during free throws such as an opponent pushing or displacing shooter or lane occupying opponent?

Im interested in a specific scenario where ball is in the air from A1 at the line and B1 shoves/displaces A2/A1. What is the correct textbook answer that I cant seem to pin down?

Ive heard both answers where shots are awarded again and Ive heard/read where ball is dead and throw in is awarded at the end line.

Thanks.