Detectives were called to a Walgreens in east Nashville the evening of April 12, after trouble developed in the parking lot.
Police told USA Today that an employee told a male team lead about two female suspected shoplifters in the store.
The lead used his cellphone to record them allegedly moving items from a shopping cart to a large shoulder bag, then walking out, police said.
One of the customers drove the other to an emergency room for surgery. The pregnant woman received an emergency Caesarean section.
WZTV reported mother Trevonsha Ferguson, 24, and her baby were in critical but stable condition on April 14. Both are expected to recover.
The name of the second suspected shoplifter has not been released, and it's not clear if she was injured.
Police have seized Boyd's pistol and phone, pending an investigation.
Authorities must decide whether the team lead's claim of self-defense is justified, or if charges will be filed against anyone.
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