A man arrested Thursday in connection with the shooting death of his girlfriend was installing a part on a loaded handgun when it fired and struck her, court documents say.

Genna Ayup, 27, was shot at a home in the 8500 block of East 18th Street around 6:30 p.m. on June 26. She was taken to a hospital, where she later died.

Her boyfriend, Ronald James Corbin Jr., 26, told police he had been at a bar from 3 p.m. until 6 p.m. and drank three to four 23-ounce beers before driving home, according to an interim complaint filed in Pima County Justice Court.

Corbin said he was putting a rubber grip on a Glock 27 handgun when it went off and hit Ayup in the head, the document said.

The couple's 2-year-old son was home at the time of the shooting.

When police arrived, they found the gun with a loaded magazine and a round in the chamber, the document said.

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Corbin told police he has many years of gun-handling experience and is a hunter.

He was booked into Pima County jail on suspicion of manslaughter.