While at work the evening of Jan. 2, a Tehachapi woman received a message from her boyfriend on Facebook stating only, "I'm sorry."

The woman repeatedly called home where the boyfriend had been left in charge of her two children, according to court documents filed by sheriff's investigators. Unable to reach him, she called her sister, who picked her up and rushed the woman to her apartment in the 600 block of Cherry Lane.

The woman entered to find her 8-month-old son dead and the boyfriend, Tobin Wayne Phillips, gone, the documents said. The other child was uninjured.

Phillips, 20, has admitted to the killing and told investigators he intended to kill himself afterward but changed his mind, according to the documents filed in Kern County Superior Court. He is being held on $2 million bail on a charge of first-degree murder.

Phillips was found within two hours of the discovery of the body of Baron Brian Smith, according to the documents, which became available Tuesday.

After authorities were called to the Cherry Lane apartment, someone at a Fastrip on Tucker Road reported a man bleeding outside the store at 1:16 a.m., the documents said. Deputies arrived to find Phillips with deep cuts to both his arms and the left side of his neck. 

Taken to a hospital, Phillips was later questioned about the injuries Phillips said he felt he deserved to die for his actions the night before, the documents said. 

"I killed my girlfriend's son," Phillips told investigators. 

He said he cut himself with a knife and started walking into the Tehachapi Mountains intending to bleed to death, but changed his mind, the documents said. He instead walked to the Fastrip and asked someone to call police.

In the four days before Baron's death, the child screamed and cried nonstop, Phillips told investigators. He said he was angry and frustrated about having to constantly watch the children, and became especially annoyed when the children's father didn't show up for a scheduled visit on Jan. 2, again leaving him with the kids. 

He said he lost his temper with Baron's crying and felt "pure blind anger," the documents said.

At about 6 p.m., he covered the boy's head with a pillow to get him to stop crying, the documents said. When the boy continued to cry, Phillips sat on the pillow until Baron lost consciousness.

Phillips told investigators Baron stopped breathing, but he managed to resuscitate him. The child then went limp in his arms, and Phillips said he placed him in a bath of cold water in an effort to revive him.

The boy was unconscious and still breathing, but "slowly drifted off" and died, Phillips told investigators.

Other injuries were apparently inflicted after Baron's death, according to the documents.

Phillips said he shook the boy after he died, striking the child's head repeatedly on the metal bar of a futon, the documents said. Investigators who examined the boy's body found several injuries to his neck and head, and a thumb-shaped bruise at the base of his jaw.

During the investigation, sheriff's detectives discovered Phillips was recently arrested outside the state for offenses similar to but less serious than the Tehachapi case.

Phillips moved in with the Tehachapi woman and her children on Nov. 23, just weeks after he was arrested in Albion, Wash., in connection with assaulting his 21-day-old daughter, the documents said. Prosecutors in Washington said the baby in that case was seriously injured, but expected to make a full recovery.

Upon being released from custody in Washington, Phillips left his fiancee and traveled to Tehachapi to stay with Baron's mother. The documents indicate Phillips had previously been romantically involved with Baron's mother, who is divorced, sometime in the past 18 months.

Baron's mother told investigators Phillips is a childhood friend she first met when she lived in Washington. She said she never witnessed him hurt the children.

Phillips is scheduled to be formally arraigned on Thursday.