SAN JOSE -- Just like she had been doing her entire life, Martha Casillas was angling for a better future for her family.

The latest leg in that pursuit was bittersweet. A better future meant taking her children and fleeing from her husband of 23 years, whose abusive tendencies hit a breaking point when he allegedly lunged at his 6-year-old son with a knife.

But police say he found them. On Saturday night he sneaked into their new home, confronted her in a bedroom, locked the door.

With his two sons watching TV in the next room, police say 40-year-old Mario Chavez stabbed her to death and shattered his own family.

Now 22-year-old Katia Chavez, their eldest child, suddenly finds herself both mourning the loss of "the best mom ever" and trying to hold onto the remaining pieces of her family: her brothers, ages 13 and 6.

"I never thought he would be able to do this," Katia Chavez said of her father. "I thought he would get mad, and that's it. I can't imagine he would do this. I just can't believe it."

She also can't believe he was out of jail in the first place, especially in light of an arrest last month after he purportedly threatened his youngest son with a knife. He made bail.

"He tried to kill my little brother, and all he had to do was pay $2,000," she said.

Mario Chavez is now being held -- without bail -- in Santa Clara County jail and was arraigned Wednesday on a murder charge. In the courtroom, he stood stoically as a judge signed a protective order barring him from contacting his two underage sons. Casillas' death marked the 36th homicide of 2013 in San Jose, and the sixth killing this year that police have linked to domestic violence.

Detective Juan Jose Vallejo, who is investigating the case, said there were likely numerous unreported incidents involving Mario Chavez. But Vallejo said police did not have the suspect on their radar until the incident that spurred his earlier arrest. He urged people who might be in similar circumstances to seek help as soon as possible.

"It's important to notify police or seek help, even if it's not police," Vallejo said, alluding to organizations that support victims of domestic violence.

Katia Chavez said her father had been angry and controlling dating back to when they lived in Mexico. Mario Chavez moved to the United States and after earning money working in construction, his family, Casillas and their two children at the time, followed. The youngest son was born here.

Mario Chavez did not have a criminal record, other than a DUI conviction. He was not in the country legally, according to police and relatives. He was arrested Aug. 12 on suspicion of criminal threats and domestic violence offenses. It was not clear Wednesday on whether those charges would have subjected him to a federal immigration hold, which would have kept him from being able to post bail.

Katia Chavez said her mother was the driving force behind the family, working long hours in inventory for a food distributor to keep a roof over everyone's head and food on the table. By all accounts, Mario Chavez was a passive provider, working intermittently.

"If he didn't feel like going, he didn't go," Katia Chavez said. "She did it all by herself. No help."

She spoke in reverential tones when describing how Casillas, 39, an avid volleyball player in her native Mexico, always had energy to do things for her children, taking her shopping and shuttling the boys to all points.

"She was always taking care of us. If she had the time, she would take them anywhere," Katia Chavez said. "The beach, the park, wherever they want."

Apparently in the background, Mario Chavez stewed, perhaps out of frustration of his own lack of contribution, relatives said. He abused alcohol and drugs, they said.

It was tolerated until the alleged armed threat against his young son last month. He was arrested, and the family moved out and got a restraining order against him. After staying with a friend, they recently moved to a home on Dakota Drive, which became the backdrop for the deadly stabbing.

A family friend heard arguing in the bedroom, followed by screaming, then silence. The friend used a credit card to open the door and saw Mario Chavez, covered in blood, coolly but rapidly making his way out of the home as his confused sons looked on, according to police.

Responding officers found Mario Chavez a short time later in the neighborhood, and he surrendered without a fight.

"Everyone is in shock," the daughter said.

Katia Chavez said that adults tried to tell her youngest brother -- the target of the suspect's previous attack -- that Casillas was in the hospital, but that he quickly figured everything out.

"He's so smart, he knows. Yesterday he cried, he said, 'I miss my mommy,'" she said.

Moving forward with a heavy heart, the 22-year-old woman who through tragedy has become the family matriarch knows what she has to do, because of the model her mother set.

"I want custody of them. I'm going to get the papers, take it to court," Katia Chavez said of her brothers. "I'm going to fight for them."

Anyone with information about the case can contact Detective Sgt. Stewart Davies or Detective Juan Jose Vallejo at 408-277-5283 or leave a tip with Silicon Valley Crime Stoppers at 408-947-STOP (7867) or with www.svcrimestoppers.org.

Contact Robert Salonga at 408-920-5002. Follow him at Twitter.com/robertsalonga.

TO HELP
The San Jose Police Officers' Association is starting a fund to support the children of Martha Casillas. For more information, go to www.sjpoa.com/Donations/Default.asp
Friends of the family have also started a fund: www.giveforward.com/fundraiser/8p13/martha-casillas-funeral-fund