(CNN) -- A Florida woman allegedly shot her daughter to death Monday night because she thought the person knocking on her door was the boyfriend she had just fought, police said Tuesday.
Witnesses told police they heard a gunshot and saw Adele Bing cradling Ruby Bing, 25, in her arms crying "Baby girl, don't die."
"How could I look my grandkids in their face and say I killed their mother?" Bing, 52, told the officers who arrested her. "Y'all can lock me away for good."
Bing is jailed on a charge of second degree murder in the death of her only daughter, according to Winter Haven, Florida, police.
The mother also faces a charge of child abuse without great bodily harm because her daughter was holding her 4-month-old baby -- the shooting suspect's granddaughter -- in her arms when the shot was fired.
The elder Bing, who was "still upset" about a "heated argument" with boyfriend James Lane earlier in the day, had "a baseball bat in her left hand and a .22-caliber pistol in her right hand" when she opened her door at 8:47 p.m. Monday, police said.
She told police it was "a f--ked up accident" because she thought it was Lane, 39, who was "banging and kicking on her front door," according to the police report obtained by CNN.
"As she opened the door, a shot was fired, hitting her daughter in the upper chest," the police release said. "The 4 month-old was not injured. Ruby Bing died at the scene."
She told police that she "intended to use the firearm to kill her boyfriend, because he stated he was going to come back and kill her," the police report said.
Lane was still at a Winter Haven hospital being treated for a head injury suffered when Bing hit him with a gun, a police statement said. Police officers were at the emergency room interviewing Lane when the call came in about a shooting at the Bing residence.
Bing is being held in the Polk County, Florida, jail.
CNN's Kim Segal contributed to this report.