Man who killed sister's boyfriend with a baseball bat was trying to protect their mother, Philly police say

A 23-year-old man fatally struck his sister's boyfriend with a baseball bat during a domestic altercation in Logan, Philadelphia police said. 

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Investigators said a woman called her mother and her brother Wednesday and instructed them to call 911 because her 32-year-old boyfriend was going to kill her, Metro Philly reported, citing a preliminary police report.  

When the mother and brother arrived at the scene on the 900 block of West Tabor Road, the boyfriend was acting aggressively, police said. During a struggle for a wooden baseball bat, the mother allegedly was hit in the head and fell to the ground. 

The boyfriend grabbed the mother and the 23-year-old man — fearing for his mother's life — struck him once in the head with the bat, police said.  

The boyfriend was pronounced dead at the scene at 5:10 p.m. Wednesday, NBC10 reported. Police and detectives are still investigating the incident.