HOUSTON -- Surveillance video captured two men who made a beer run in a stolen car minutes before one of them stabbed a woman to death as she tried to stop him from taking her vehicle with her 4-month-old daughter inside, Houston authorities said.

Harris County sheriff's deputies said Tina Davila, 39, was fatally stabbed in front of a Cricket cellular store in northeast Harris County at about 5 p.m. Wednesday, reported KPRC-TV in Houston.

"Apparently the victim had left her child, small child, in the vehicle as she ran in to pay her phone bill," Sgt. Bryan Pair said. "That's why she was attempting to take her keys back from the suspect. Based on what our witnesses tell us, that she was pleading for her car keys back; that he couldn't take her car, that her baby was inside the car. That's why she was fighting over the keys. That's when he stabbed her one time."

Davila died at a nearby hospital from a stab wound to the chest.

Surveillance camera video captured from inside the cellular store showed Davila getting out of her car, then a gold Ford Taurus driving up beside her. A man got out and stole her keys. The video showed Davila fighting back before the man fled in the Taurus.

Davila's sister-in-law said watching the video of the attack was heartbreaking.

"She just drove up and they just drove right behind," Mary Foster said. "I don't know if they were following or if it was just like, 'Hey, let's go get that.' I'm not really sure. It's just so many things that could have happened and no one knows."

Deputies said a man stole beer at a Houston-area convenience store five minutes before the killing. He and another man were using the same stolen car seen in the surveillance video from the cellular store, officials said.

"We have learned that the vehicle that they used was taken in a carjacking in the city," Lt. John Denholm said.

Denholm said the man who ran out of the store with the beer was the same man who stabbed Davila and they were caught on surveillance video at the store.

Investigators are trying to find the stolen 2002 gold Ford Taurus with Texas license plate P42 CYY. Detectives want to find the attacker and the man who was driving the car, both of whom are considered armed and dangerous.

Davila's daughter was not injured. She is staying with family members. Davila had four other children -- three teenagers and an 8-year-old girl -- and was engaged to be married.

Davila's fiancé said he was grateful to her for saving their baby.

"Strong, strong person -- real strong, happy, lovable, loved one another. Everything was the kids and the baby," Billy Brewer said.