Harris County detectives are asking for the public’s help to find the gunman who killed a 4-year-old girl and shot her sister and mother.

They released a photo of a vehicle they believe is connected to Ava Castillo’s murder. It is a black Honda Accord with license plate GBV0987. The vehicle was taken in a reported carjacking the same night Ava was shot to death.

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.

KHOU 11 News has learned that Diana Gomez was shot seven times during the violent ambush at the Mission Falls Apartments.

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.”

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

Gomez was struck by seven bullets. She remains in critical condition and relatives say she can’t stop crying over the death of Ava. Betzida was also shot but she has been released from the hospital.

The shooting happened just before 9 p.m. at the Mission Falls apartments in the 10400 block of Greens Crossing Boulevard.

Investigators are looking at nearby surveillance video for further clues. They are also looking into whether this case could be connected to other violent robberies in the area.

Deputies questioned a man about the case on Tuesday but he has been cleared.

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(8477). Crime Stoppers will pay up to $5,000 for information leading to the charging or arrest of the suspect(s).