A 9-year-old boy arrived at school Monday with a grisly story: His mother and sister were dead at their home four blocks away.
Minutes later, police found the bodies of a 10-year-old girl and her mother _ along with a blood-covered father and an unharmed 4-year-old boy _ in a modest home in a West Las Vegas neighborhood, authorities said.
The five people belonged to a single family, police Officer Jacinto Rivera said.
The man, who was hospitalized with a head injury, was not immediately identified as a suspect or charged.
Police wouldn't immediately say how or when the slayings occurred, but Rivera said there was no immediate evidence of a break-in at the home or that a suspect was on the loose.
One neighbor, Lucinda Jackson Griffith, said she heard at least one gunshot early Monday.
Longtime neighbor, Dick Webb, said he had walked past the home less than 90 minutes before the boy arrived at school. He said he didn't notice anything amiss.
Rivera called it too early in the investigation to determine a motive, and said investigators were working carefully to collect evidence inside the single-story stucco home with a motorcycle and two sport utility vehicles in the driveway.
"We get one shot at a homicide scene. Our No. 1 priority is to find out what happened," the police spokesman said. "Right now we don't know what happened."
Clark County spokesman Erik Pappa said the 4-year-old and 9-year-old boys were in the custody of child protective services because they didn't have an adult caregiver.
Clark County Department of Family Services officials planned to try to locate other relatives before placing the boys together with a foster family, department spokeswoman Christine Skorupski said.
Police cordoned off the entire block near the home during their investigation.
Officials said the boy was uninjured when he arrived at Mabel Hoggard Elementary School, where his older sister also was enrolled.
Principal Celese Rayford declined comment.
Clark County School District spokeswoman Amanda Fulkerson wouldn't describe how or what the boy told school officials, or whether other students were told what happened.
School administrators quickly notified police about the boy's story and began mobilizing its crisis response team to help students process the tragedy, Fulkerson said.
The campus, with about 450 students in grades kindergarten through 5, was "struggling to sort out emotions and details of a tragedy that claimed the life of a student at home this weekend," she said.
Students also were being reminded that school "is always a safe zone with caring adults that can help in uncertain situations," Fulkerson said.