It happened around 11:15 p.m. Sunday on the 9500 block of Clark Street.
The man called police and told them he was cleaning his gun when it went off.
A bullet struck his 22-year-old girlfriend in the neck.
She was taken to the hospital where she died a short time later.
Police found multiple weapons in the second floor of the home.
Investigators were questioning the boyfriend. No charges have been filed at this time.
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