A 6-year-old Dallas girl was fatally shot at her family’s home Wednesday afternoon with an unattended gun while her mother was at a mortuary planning a funeral for her 14-year-old brother, who died after being shot on Dec. 29.

The Dallas Police Department said the girl, identified by family as Ah’Laynah Modica-Ross, was taken to the hospital shortly before 3 p.m. Wednesday in critical condition and later died of her injuries. Authorities have not yet revealed how she was shot but said two adults and two other children were home with her at the time.

Damariya Sowels, 19, was arrested on suspicion of tampering with physical evidence and over unrelated warrants. Investigators said he told them that he brought two guns to the home and left one, a MAC-10, unattended on top of a PlayStation game console in a bedroom on the third floor. 

According to information from police included in an arrest affidavit obtained by HuffPost, Sowels said he went upstairs after the shooting and retrieved the MAC-10 before investigators arrived. He allegedly put it in a backpack along with the other gun, a Glock 40, and hid it in the garage, where crime scene investigators later found it, the affidavit says.

Ah’Laynah’s older brother Ah-bralen “Bra” Rider was shot Dec. 29 at a friend’s apartment and died on New Year’s Eve, authorities said. Another 14-year-old he was with was also shot but was expected to survive. A 16-year-old boy, whose name has not been released because of his age, was arrested in relation to the shootings.

Last week, Brittney Ross, the children’s mother, spoke about her son’s death in a television interview with Dallas station KTVT-TV with Ah’Laynah by her side. On Tuesday, she told the CBS affiliate that she was “overwhelmed” by the loss of her two children and that the funeral for Ah-bralen, originally planned for Saturday, would be postponed so the two could be buried together.

In a GoFundMe campaign to raise money for funeral expenses, a relative said Ross has four surviving children.

The siblings’ grandfather Michael Key toldreporters Thursday that the family was “living in a nightmare right now.” Ah’Laynah had just turned 6 on Dec. 27 and still hadn’t unwrapped all of her presents.

“Dealing with the loss of two grandbabies back-to-back, it’s hard right now,” Key said, “especially this little one,” referring to Ah’Laynah, who he said was “very sweet, very smart — highly intelligent.” 

“This was my heart,” he said.