Police say a man who pulled over to help a bleeding 10-year-old boy by the roadside likely saved another boy's life by intervening in a mother's knife attack on her son.

Robert Villarreal, 46, was departing San Antonio for Eagle Pass on Tuesday for his job as a U.S. Customs and Border Protection officer when he saw the 10-year-old covered in blood.

The boy told the man his mother was stabbing his brother inside a nearby house. Villarreal instructed another motorist to call authorities while he followed the boy to the house.

Villarreal said he entered the home's back door to find the woman holding the 12-year-old boy's neck with one hand and clutching a knife and a fork in the other. The kitchen floor was splattered with blood.

"She was hysterical," Villarreal said. "She said she was going to kill the little boy. She had already stabbed his brother and she was going to kill him."

Villarreal managed to wrestle the woman to the ground, separate her from the boy, retrieve the knife and then drag her outside. He said the woman was upset and disoriented.

"If (Villarreal) had not stopped, at least that one little boy that was inside would have died," said San Antonio Police Department spokesman Joe Rios.

Police arrested the boys' mother, 48-year-old Maria Alsareinye, in the stabbings, Rios said. She was charged with two counts of injury to a child causing serious bodily injury, a first-degree felony. Her bond was set at $300,000.

The 10-year-old boy was taken to a hospital in critical condition. The 12-year-old boy was hospitalized with less serious injuries, police said. Both children were in stable condition Tuesday afternoon, hospital officials said.

Villarreal said his assistance was "something anybody in my position would have done." He praised the boys for protecting themselves. The 12-year-old managed to keep his mother's knife away from his throat, Villarreal said.

"He did actions that probably saved his life," Villarreal said. "Both of them. The other one had the presence of mind to go out and get out of the house."