A 35-year-old Nebraska man apparently drove to the Bay Area after killing his two small children amid a custody dispute with his estranged wife, and he was arrested Sunday in Pacifica.

Following two welfare checks in which police arrived at his seemingly empty home in Bellevue, Nebraska, south of Omaha, they were called back to the home Sunday morning after family friends gained access to the home and found the children dead. A cause of death has not been given, but the Associated Press reports that the remains of 5-year-old Emily Price and 3-year-old Theodore Price were found in the home, which belongs to their father, Adam Price.

The children were staying with Price during a week of visitation, and their mother in Illinois, Mary Nielsen, became concerned Saturday when she had not been able to FaceTime with the kids since Thursday evening.

After police said Sunday morning that they did not "observe exigent circumstances that would allow them to force entry into the home," friends of Nielsen entered the home and made the gruesome discovery.

"I’m not sure if they forced entry or how they got in, but the friends were actually the individuals that found the children inside and they contacted police and we responded after that," said Capt. Andy Jashinske of the Bellevue Police Department in a statement.

The two deaths likely occurred between Thursday and Saturday, and Price appears to have then made the 25-hour drive from Nebraska to the Bay Area. It's unclear how authorities tracked him down in Pacifica.

Neighbors of Price say they saw the kids playing outside on Wednesday, but not after that. And some told local station WOWT that it was strange when Price put out his garbage bins on Thursday, when trash pickup in the neighborhood doesn't happen until Monday.

As the Daily Beast reports, Price has not yet been charged with the children's murder, and authorities have only said so far that the deaths are "suspicious."

A devastated Nielsen has posted on Facebook since the discovery of the children, saying, "I’m so sorry to see you two go. You did not deserve this and I love you so very much. I would fight a thousand fights to have you back again."

Nielsen's divorce was apparently not yet finalized, and she wrote that she had "spent every penny I have trying to get them back in my full custody."

“Heaven gained two beautiful angels and I hope great grandpa was at the gates to greet you," she wrote. "You were the only reasons I survived everything I did and the only reason I am alive. I love you. Til we meet again my sweet babies."

A relative, Nichole Nielsen, has set up a GoFundMe to assist with funeral expenses.

"Emi and Teddy were some of the sweetest most loving children and did not deserve to leave the earth this way," she writes. "Not only does Mary have this burden but she now has 2 funeral expenses to cover."

Price has been booked into Maguire Correctional Facility in Redwood City on a felony fugitive arrest warrant. As KETV Omaha reports, he is scheduled to appear in court at 1:30 p.m. PT on Monday.