Police shot and killed a woman on a busy thoroughfare Tuesday after authorities said she created a disturbance in a fast-food restaurant, walked into traffic with a child and threatened motorists with a knife.

Officers pulled a boy about 3 years old away from the woman and used pepper spray, Taser guns and beanbag shotgun rounds to try to subdue her before two officers shot her at about 8 a.m., said Officer Jose Montoya, a department spokesman.

"She tried twice to get into two different vehicles showing the knife," Montoya said.

The woman, who was not immediately identified, was shot twice and was pronounced dead at a Las Vegas hospital, authorities said.

The child was unharmed, Montoya said. He was placed in the custody of Clark County child welfare authorities. His relationship with the woman was not immediately known.

Officers were first called at about 7:50 a.m. about a woman creating a disturbance at a Jack In The Box restaurant, Montoya said. No customers and no police officers were hurt.

The woman, with the child in tow, walked onto Martin Luther King Boulevard, a key route between North Las Vegas and downtown Las Vegas.

Officers diverted the woman's attention and managed to pull the child to safety before she was shot.

Several blocks of the road near Lake Mead Boulevard, about four miles north of the Las Vegas Strip, remained shut down for hours while police interviewed witnesses and collected evidence.

It was the second fatal shooting in a week involving Las Vegas police, and the third officer-involved shooting in three weeks in southern Nevada.

A Las Vegas police sergeant shot and killed a 24-year-old man last Wednesday after interrupting a robbery in progress outside a convenience store, authorities said.

An officer in neighboring Henderson was wounded in the leg May 30 when he and several other officers exchanged gunfire through the bedroom door of a home where an armed man fired shots during a domestic dispute. The gunman and his estranged wife were later found dead in what police characterized as a murder-suicide.