Nikolay Soltys has confessed to killing his pregnant wife, 3-year-old son and four family members, police sources said Friday morning.

The 27-year-old Ukrainian immigrant was captured in his mother's backyard in Citrus Heights, Calif., Thursday after a 10-day international manhunt.

Soltys told police his family members were "poisoning" him. Officials are trying to determine what he meant by that.

Soltys was in the yard crouched under a desk, dirty and barefoot, when his brother Stepan saw him through a window. It was 7:45 a.m. Thursday.

Soltys motioned for him to be quiet, but Stepan instead gathered his family into the garage and grabbed for the police-installed panic button. When the alarm failed, the family piled into the car and drove to a nearby shop, where a clerk called 911.

Within minutes, sheriff's deputies stormed the yard and arrested Soltys, one of the FBI's 10 Most Wanted.

The family's fear was so intense, police said, that Stepan at first refused to return to the house to identify Soltys.

"He was obviously extremely afraid," Deputy Sheriff Bill Samuelson said.

When Soltys was arrested, he had a metal potato peeler in his pocket and a map of the Sacramento area. Officials said a backpack containing a knife authorities suspect was the murder weapon was found in the yard.

Sacramento County Sheriff Lou Blanas said later Thursday that Soltys was speaking freely to prosecutors, though he did not yet have a lawyer. Blanas did not provide details.

Police have said that a note Soltys left in his car suggested the relatives were killed because they spoke outside the family about private matters. Some in the Ukrainian community have said that may have meant he thought they were "poisoning" his name, The Sacramento Bee reported.

"When I learned that Nikolay was captured, I was in shock," said Boris Kukharskiy, Soltys' cousin and the father of one of the children slain. He and family members had moved to a hotel under constant police protection.

"From day one of this tragedy to the last moment, they didn't leave us, even for a second," said Sergey Kukharskiy, another cousin and the father of another young victim.

Authorities interviewed Soltys for several hours before he was taken to Sacramento County Jail. He was expected to be arraigned Tuesday.

The manhunt began the morning of Aug. 20, when authorities say Soltys slashed the throat of his 23-year-old wife, Lyubov, at their North Highlands home.

Police say he then drove to the home of his aunt and uncle, Galina, 74, and Petr Kukharskiy, 75, and killed them and their 9-year-old grandchildren, Tatyana and Dimitriy Kukharskiy.

The following day, notes left in Soltys' abandoned car led police to a rural trash pile where they found the blood-covered body of his 3-year-old son, Sergey, in a cardboard box.

More than a dozen of Soltys' other relatives had remained under police protection since the slayings. Soltys' mother, brother and a few other relatives had only returned to her home Tuesday.

Undercover detectives had been watching the house around the clock, but never saw him. Just before 8 a.m. Thursday, they saw the garage door fly open and the car speed away.

At the framing shop a few blocks away, employee Jennifer Murphy saw Stepan jump out of the car, clearly panicked and shaking as he tried to dial a number on a cell phone.

"He kept pushing buttons 1-1-9, so I knew he wanted to dial 911," Murphy said. "I brought him into the store and dialed 911 for him."

The deputies who stormed the cluttered yard minutes later saw Soltys' feet sticking out from under the desk, which was next to an old refrigerator.

"He appeared as if he was going to run, but the inoperable refrigerator door was open, blocking his exit," Sheriff's Detective Chris Joachim said.

Authorities said they believe Soltys had been staying in woods behind the house for a few days. An officer had checked the yard Wednesday evening, Blanas said.

"At night there's so many ways to get into that back yard, you can't cover every inch," Blanas said.

The Associated Press contributed to this report.