Walter and Lee Began Making Plans to Rob a Neighborhood

Walter and Lee began making plans to rob a neighborhood bank. Barry agreed to be the lookout and the getaway driver as long as he got a percentage of the stolen money. Last Wednesday, Walter and Lee entered the Hillcrest Fields Bank wearing ski masks and armed with pistols. After 10 minutes, Walter and Lee left the bank with bags of cash and began to run toward Barry's getaway car. However, they were confronted by a security officer who chased Walter and Lee from the bank. Walter fired his pistol at the officer, killing him. Which of the following is true?

A) Under the common law, Barry is liable as a principal in the second degree.
B) Under the mere presence rule, any bystander in the bank who watched the bank robbery take place is an accomplice.
C) Barry is not responsible for the security officer's death under the natural and probable consequences rule.
D) Only Walter is responsible for the death of the security officer.