PHILADELPHIA The mother of a 2-year-old boy who accidentally shot and killed his 11-year-old sister with a gun found under their mother's bed turned herself in to police Thursday.

Tiffany Goldwire, 31, of West Philadelphia, was being charged with involuntary manslaughter, endangering the welfare of children, and weapons offenses, police said.

Goldwire's daughter, Jamara Stevens, died April 5 after she and her siblings found a cocked and loaded .357-caliber revolver in Goldwire's bedroom.

Goldwire's boyfriend had left the gun on top of a refrigerator earlier in the day, police said. Goldwire then told Stevens' 14-year-old sibling to move the gun to a "safe place," said Lt. John Stanford, a police spokesman.

The teenager placed the weapon under Goldwire's bed, where the younger children found it. In her initial statement to police, Goldwire told police she left the children to play in the room while she used the bathroom. Police say the 2-year-old managed to squeeze the trigger; they found powder burns on his hands. The bullet passed through Jamara's chest, killing her.

On Wednesday, the District Attorney's Office said it had approved charges against Goldwire because she was the adult in the home and had been reckless with the gun.

Stanford said Goldwire has not helped police locate the boyfriend who left the weapon. Police have identified the man, Stanford said, but cannot find him.

"She hasn't cooperated in any way that you think a person would," Stanford said.

Goldwire's attorney, Eugene Tinari, said Thursday that Goldwire was in a "state of disbelief and depression."

"She is living a nightmare," he said. "Adding to that, she is now under arrest and they are attempting to blame her for the death of her daughter."

"She wants to get back to the rest of her family to mourn the loss of her daughter."

Jamara's three siblings have been staying with relatives, Tinari said.

He said he believed police had arrested Goldwire in an effort to get information about "the ownership of the gun."

He said Goldwire would not give a statement to police Thursday.

"What comes down the road in terms of cooperation will have to be seen," Tinari said. "But if there is someone who should be held accountable for leaving the gun and she knows who it is, she isn't going to try and protect anyone."

Goldwire has eight previous arrests for weapons, theft, and assault charges. In 2009 she pleaded guilty to illegally possessing a firearm and was sentenced to 23 months in prison.