Updated

Police have not determined what drove a man to allegedly attack his bedridden sister-in-law with a medieval-style battle ax and then go on a rampage outside a Las Vegas home, hacking a 4-month-old baby to death and critically wounding the child's mother.

"We don't know why he wanted to injure the woman or why he attacked the people on the street, just that he did," Las Vegas police homicide Sgt. Russell Shoemaker said Friday. "We'll figure this out some day. For right now, all we have is theories."

Harold E. Montague, 33, told investigators he remembered nothing about the attack, and police said he didn't know the woman or the boy he is accused of hacking with the blade of an ax before noon Thursday on a sunny street east of Las Vegas Boulevard.

"He claims he blacked out. He said he doesn't remember anything," police homicide Lt. Lewis Roberts said. Montague was interviewed by homicide investigators and taken to a hospital before he was booked into the Clark County jail.

"We don't know what set him off," Roberts said.

Police were awaiting blood test results determining whether Montague may have been under the influence of alcohol or drugs. Roberts said he admitted smoking marijuana but didn't say whether he had taken other medications or alcohol.

Montague is accused of stabbing his 36-year-old mentally and physically disabled sister-in-law, Monica O'Dazier, more than 20 times with the pointed end of a ceremonial ax before bursting out of his home into the street.

Shoemaker said Montague swapped one weapon for another one like it before going outside.

A neighbor said she couldn't believe what she was seeing as Montague attacked the baby and the child's mother.

"I told him to stop. He just reared up and looked at me," said Teresa Garner, a 52-year-old former hotel worker who said she doesn't remember Montague saying a word before he returned to swinging the menacing-looking weapon like a golf club.

Garner called the police emergency dispatcher and Montague retreated back inside his rented white cinderblock home across the street.

As police arrived, Montague emerged empty-handed, taunting officers with profanity and trying to wrestle a shotgun from the hands of an officer, according to a police report. Police shocked him with a Taser to help subdue him.

Garner said she wanted to help the baby in the overturned stroller next to a widening pool of blood near the end of her driveway. She said she also tried to keep the severely wounded and disfigured mother from trying to stand.

"I'm surprised she lived," Garner said of the woman, identified by police as Sandra Lisset Castro, 28. "Her whole face was gone. She had a big gaping wound on the top of her head."

"She kept saying, 'Help my baby! help my baby!"'

Garner said it was obvious the child was already dead. The Clark County coroner reported that 4-month-old Damien Avila-Castro died of multiple head wounds.

Police said Castro was taken to Sunrise Hospital and Medical Center in very critical condition. Hospital spokeswoman Ashlee Seymour said Friday she had no patient by that name.

O'Dazier was taken to University Medical Center in Las Vegas, where hospital spokeswoman Danita Cohen said Friday she was in fair condition.

Two children, ages 2 and 6, were found in the house unharmed, police said.

Montague's wife was at work at the time of the attack, and a 15-year-old daughter was at school, Shoemaker said. No one was at the house Friday.

Garner, who lives with her mother, said Montague and his family moved about a year ago into the corner home on a dirt lot with spray-painted white van parked against the garage.

Montague was held without bail pending a court appearance Tuesday on charges of felony murder, attempted murder and attempted murder of a police officer. Court officials said it was not immediately clear if he had a lawyer.

Roberts described Montague as the caregiver for his sister-in-law.