HARRIS COUNTY, Texas -- Sources within the Harris County Sheriff's Office tell KHOU 11 News that two people are being questioned in the shooting death of 4-year-old Ava Castillo earlier this month.

Detectives have been questioning two men, their ages and identities are still unknown. The men were taken into custody on Tuesday. Charges have not yet been filed.

Ava and her 10-year-old sister, Betzida, were helping their mom, 27-year-old Diana Gomez, unload groceries when the suspects ambushed them and tried to grab Gomez’s purse. The shooting happened at the Mission Falls apartments in the 10400 block of Greens Crossing Boulevard.

RELATED: Community remembers 4-year-old at vigil

Later, detectives said the vehicle used in the robbery and shooting was found in northeast Harris County.

Sister Julie Gomez said Diana “did not resist” when the attackers tried to yank her purse away, contrary to preliminary reports from authorities.

“They ran up on her. There were three men. They tried to steal her vehicle. Once they couldn’t start the vehicle, they went for the purse,” Julie Gomez explained. “The shooter was wearing a rag or mask. He just started shooting when he couldn’t get the purse off her.”

She said Diana did everything in her power to protect her children.

“She saw the gun and tried to put the kids behind her,” Julie Gomez said. “My sister is at a loss for words. She’s in shock. She’s in disbelief.”

Diana is now out of the hospital after she was shot seven times.

Ava and Betzida Castillo and their mom were shot during a robbery in northwest Harris County. Ava, left, didn't survive. 

It's not clear whether the persons of interest in custody potentially have only information about the vicious attack or if they were directly involved. Sources say they don't want to disclose information at this time because they don't want to do anything that could jeopardize the investigation.

Ava Castillo's family says they are waiting to hear from detectives, hoping and praying that authorities are close to finding justice for the family. However, a source close the investigation says that there likely won't be new developments until at least Thursday.

Anyone with information is urged to contact the Harris County Sheriff’s Office Homicide Division at 713-274-9100 or Crime Stoppers at 713-222-TIPS.