Chicago police say they've arrested a man in the slaying of an 11-year-old girl who was struck in the head by a stray bullet while at a sleepover last week.

Janel Sedevic, a Chicago police spokeswoman, says the man has been arrested on a first-degree murder charge and will be formally charged Thursday. She provided no other details.

Sedevic says Superintendent Garry McCarthy will discuss the arrest at a Thursday morning news conference.

Shamiya Adams was making s'mores at a friend's house in the West Garfield Park neighborhood on July 18 when she was struck by a bullet. She died early the next morning.

Police have said the gunman may have been firing at another person in a gang dispute outside the house.