A man repeatedly stabbed his toddler and estranged wife along an interstate while horrified people watched from their cars in rush-hour traffic Friday night, police and witnesses said.

The 2-year-old girl was in a car with her parents when her father started stabbing his wife with a kitchen knife along Interstate 110 near the Governor's Mansion, said Cpl. L'Jean McKneely, a Baton Rouge Police spokesman.

When the 26-year-old woman got out and ran for help from an East Baton Rouge Parish sheriff's deputy in squad car just ahead of them, her husband stabbed his daughter, McKneely said.

"He kept stabbing her until the knife was stuck in her head," witness Gloria Spears told WAFB-TV.

The man then put the girl on the highway and drove off, side-swiping the deputy's car and striking his wife, police said. He sped into downtown Baton Rouge and knocked down at least three utility poles before his car hurtled through the air and overturned on top of another vehicle.

All three were taken to Our Lady of the Lake Medical Center. The child was in "extremely critical" condition, with a cut "along her midsection and a kitchen knife lodged in her head," McKneely said.

Her mother, who was thrown 20 to 40 feet by the impact of the car, also had numerous stab wounds, he said. She was expected to live. The man was being treated for minor injuries, McKneely said.

McKneely said the couple, who was not identified, has been married for about six years but were currently living apart. It was not immediately clear what led to the stabbings.