HOUSTON -- It's a difficult video to watch. It shows Tina Davila, a mother of five, as she walks toward a mobile phone store.

A man grabs her car keys and they struggle. She tries to get the keys back, and that's when he stabs her, repeatedly and leaves her for dead.

Davila made it into the store, but the 39-year-old died at the hospital.

"They're gonna pay,” said Billy Brewer, Davila’s boyfriend. “I'm gonna do what I can do.

“They're gonna pay.”

Davila is the mother of his 4-month old daughter. The little girl who was in the backseat of her SUV when she was stabbed.

Courtesy photo

Tina Davila was stabbed to death as she tried to protect her 4-month-old from a carjacker.

She fought off the attacker because the little girl was in the car.

"What any other mother would do, protect the baby,” said Brewer.

But her fight to protect the baby was only caught on a grainy surveillance tape, which is not enough to find the killer.

But Don Nguyen did catch him five minutes before the murder. Police say the same man was at Nguyen's convenience store several miles away.

A Hispanic male, his face captured clearly on camera, as he steals a case of beer and then drives toward Tina Davila's murder.

The man in the blue shirt is one of two suspects investigators are looking for.

Witnesses described the suspects to be two men in their mid to late 20s. Investigators determined that the suspect vehicle is a 2002 Ford Taurus with the Texas license plate number P42-CYY.

The camera that captured the best image of the suspect was one of 16 installed just a month ago.

Photo from surveillance video

Deputies have released descriptions of the suspects and their car in the murder of a mother outside of a northeast Harris County cell phone store.

"I think anything can help catch the killer for the victim, we be happy to help,” said Nguyen.

"I don't really want to even go home right now,” said Brewer. “It's too much memories.”

In his grief, Brewer is thankful for those few images of video, images to help catch the thug in the blue shirt.

The other video, however, he will not watch. He can't stand to watch the end of his girlfriend's life.

"They're gonna pay,” he repeated. “I'm gonna see to it. Whatever it takes."