STOCKTON — Don Policarpio and his mom, Roselyn, had made plans to get together Thursday. But when he called her phone in the afternoon, Policarpio said, her husband, Gregory Prokopowicz, answered and delivered a chilling message:

“You’ll never be able to speak to your mom again,” Prokopowicz calmly said. “I killed her.”

That was sometime around 1:40 p.m., Policarpio said, about 10 minutes after police were called to First Avenue in Walnut Creek, where a woman, later identified as Roselyn, had been shot multiple times. Medical personnel could not save her life.

After shooting Roselyn, Prokopowicz drove away before officers could arrive, police said. Roughly five hours later, they found him in Martinez, initiating what would become a 19-hour standoff with police before he was finally taken into custody. On Tuesday, prosecutors will review the case and are expected to file a murder charge.

At first, her son didn’t believe the words he was hearing, but he did believe Prokopowicz was capable of committing such an act. It wasn’t the first time he had been physically abusive to his mother, Policarpio, 25, said during an interview Monday at the family’s Stockton home. And it wasn’t the first time he had made threats to their family.

For the past several months, Prokopowicz’s behavior had become increasingly volatile and more violent, capping a tumultuous, two-year relationship between the couple that often was punctuated with loud arguments, frequent crying bouts and declarations from Roselyn, 47, that she was leaving him.

“That’s why I got scared,” Policarpio recalled. “(His voice) was, just, cold.”

The descriptions are similar to a 2007 restraining order filed against Prokopowicz by his ex-wife. The woman, whom this newspaper is not naming, wrote during their one-year marriage that Prokopowicz abused her verbally and physically. She also alleged Prokopowicz asked her to buy a gun for him but that she refused.

The Policarpio family is close. They spent every Saturday together attending the Church of God International in Fremont and watching Running Man, a Korean variety show, on Sundays. But Prokopowicz, 38, didn’t like the time she spent with her kids and would often get angry when she did, Don Policarpio’s brother, Angelo, said.

Roselyn’s three sons and daughter, who range in age from 18 to 25, were born and raised in a Manila suburb, where they lived with her and their father, Armando, Angelo Policarpio said. They moved to the United States in 2008, when Roselyn’s employer, Cypress Semiconductor Corp., asked her to relocate to the Bay Area. She had been working a graveyard shift for the United States-based company for the better part of the past five years, and it was beginning to wear on her, he said.

“It was exciting,” Angelo Policarpio, 24, recalled. “It was a whole new experience, a whole new world.”

The family lived for several years in Milpitas and San Jose before moving to Stockton in 2013. Roselyn eventually left to work for McAfee, and later, the American College of Nursing in Concord. But the grueling commute from Stockton to Concord was too much, he said.

She asked her family whether it would be OK if she rented a room with a coworker closer to her office and came home on weekends. Her then-husband, Armando, agreed. Though looking back, he said he wished he hadn’t.

“That was my biggest mistake,” he said, “because that started all this mess.”

At some point after that, Roselyn met Prokopowicz, who was then a student at the nursing school. His name started to come up in conversation, whether she was giving him a ride home or helping him in other small ways, he said. When Roselyn told Armando she was beginning to fall in love with Prokopowicz, he knew their marriage of 28 years was over.

“It was too late when she told me that,” he said. “I was heartbroken. But there was nothing I could do except let her go.”

Still, Armando said, he knew there was something wrong with the new relationship.

“He wasn’t just in love with her,” he said. “He was obsessed.”

And then Roselyn changed. The frequently sunny and smiling woman who would spontaneously break out into song began to withdraw. She cried often. She became protective of her phone, Angelo said, never letting it far from her hand. When she spent time with her children, she was aloof.

“Physically, she was there, but you could tell her mind was somewhere else,” he said. “It felt like she was lonely.”

In January 2016, the couple moved to Anchorage, Alaska, Angelo said. By that point, Roselyn had been fired from her job at the nursing school, and Armando said Prokopowicz had lost his job as well. They wanted a new start and got married, Angelo said, though he said he didn’t know whether she ever legally adopted her new husband’s surname.

It was also during that time that Roselyn began calling her children in tears. She told them Prokopowicz beat her, her daughter Yvette, 18, said. She begged her mom to leave him. Angelo told her he would call the police for her from California. Roselyn pleaded with Angelo not to involve the authorities. She told her children she would escape when she had the chance.

Sometime in July, she did just that and stayed with her children at their Stockton home for three weeks, sleeping curled up next to Yvette. But Prokopowicz was not far behind. And Roselyn ultimately went back to him.

In January, the threats began, Angelo said. Prokopowicz was becoming more and more unstable and would call Angelo just to swear at him. He made thinly veiled threats, saying, “I want you to know I know where you live,” Angelo said.

“He would just go off randomly,” Angelo said. “I was angry. I told him I know where he lives, also.”

It’s unclear what led up to the final moments of Roselyn’s life. But, on Tuesday, she visited her children and told Don she was leaving Prokopowicz, who police believe was living part time in Walnut Creek, for good. On Wednesday, she made pancit, a Filipino noodle dish, and, although she was breaking up with him, saved a portion for Prokopowicz that she planned to bring to him the next day. She kissed her children, promising to meet Don after work and Yvette after school on Thursday.

She told Angelo, “You still a need a mom.” And then she said goodbye.

The family has established a GoFundMe campaign to raise money for Roselyn’s funeral expenses, which can be accessed here.

Staff writer Nate Gartrell contributed to this report.