A good Samaritan could not save a Las Vegas woman screaming for help as her gun-wielding husband chased her from their home to two drug store parking lots in a chaotic murder-suicide that left a family of five dead, authorities said Thursday.

The man gunned down his wife outside a business and killed their children, ages 9 to 15, at their apartment before shooting himself at the home, police said. Homicide detectives are investigating what drove him to kill his family.

"It's really hard to understand how this could happen, how somebody could do that to children," police Lt. Dan McGrath said.

The Clark County coroner's office identified the woman and children as Phoukeo Dej-oudom, 35; Dalavanh Ariel Dej-oudom, a 15-year-old girl; and two boys, Anhurak Jason Dej-oudom, 9, and Xonajuk J.J. Dej-oudom, 14. The father has not been named.

A driver spotted the woman waving her hands and screaming for help in the street near her home and picked her up Wednesday night. The father chased them to a CVS drug store two blocks away, where he dragged his wife into his car at gunpoint.

As he drove off, his wife partially hung out the window and eventually escaped and started running. Witnesses saw the man chasing her in his car while she fled toward a Walgreen's about a half mile away.

Witnesses outside the store reported hearing four gunshots, and a bystander rushed to the woman, but she was already dead, with least one gunshot wound to the head, McGrath said.

The man fled. A relative called police half an hour later saying the man was at the apartment and suicidal.

A SWAT team responded and found the bodies of the father and three children in a bedroom, though authorities were not sure if he killed the children before or after his wife.

Domestic violence reports involving the family were noted earlier this month at the same apartment and in an out-of-state incident a decade ago, McGrath said.

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This story has been corrected to show that the bodies were found Wednesday night, not Thursday.