ESTACADA, OREGON - Police said a man who stabbed and wounded an employee inside a grocery store in the north-western US state of Oregon on Sunday (May 14) was carrying his mother's severed head.

In a statement on Monday, police said the officers who responded to the incident on Mother's Day determined that the woman's head belonged to 59-year-old Tina Marie Webb, whose body was found at her home in Colton, Oregon, about 19km away.

A 911 caller told police the man walked into Harvest Market Thriftway in Estacada around 2.15pm. He was "covered in blood" and holding "a knife and what looked like a human head", US broadcast station KOIN reported.

Witnesses said the suspect stabbed a store employee who was airlifted to a medical centre with critical injuries. Other workers held the suspect down until the authorities arrived and took him into custody.

Police described the suspect as "catatonic", reports said.

They later identified him as 36-year-old Joshua Webb. While police said the man killed his mother at home, they did not provide more details.

The suspect has been booked on charges of murder and attempted murder in the case. He has not yet made a court appearance.

A relative discovered the woman's body at home and called 911 about 15 minutes after the grocery store stabbing attack, reports said.

The suspect's father, Mr David Webb, was not home at the time his wife was killed, The Oregonian newspaper reported.

"My wife was wonderful," he was quoted as saying on Monday.

"I've been married to her for almost 41 years. Joshua was our son. I never saw a problem. Evidently there was one. I don't know. I start crying every time I think about it."

His wife had said she believed her son - who had vision problems and had been living with them at home - was depressed, reported Associated Press.

"I just can't believe I lost my wife and son in one day... I wish I had some answers, but I don't. I waited all my life to retire with my wife, and now I can't," he said.