A security guard was knocked unconscious and suffered serious head injuries in an incident that started at a Marks & Spencer branch and spilled over into the nearby car park.
The man, believed to be aged in his 50s, is thought to have been giving chase to a suspected shoplifter when he ended up on the ground at the busy Weavers Wharf shopping centre in Kidderminster.
Staff at the nearby Pizza Hut restaurant later saw him lying in a parking space, covered with a blanket and surrounded by police officers.
He was airlifted to the Queen Elizabeth Hospital in Birmingham.
A man was arrested nearby shortly afterwards and no-one else is being sought by officers following the incident, which happened at around 11am.
Supt Kevin Purcell, of West Mercia Police said: “This inquiry is at a very early stage and we are trying to ascertain what happened.
“The incident took place in a busy shopping environment and we are aware there were a number of people in the vicinity, some of whom may not have realised the significance of what they saw.
“We are appealing for any witnesses who saw anything in the store or car park who haven’t already spoken to police to contact Kidderminster CID."
A West Midlands Ambulance Service spokeswoman said: “The man, a security guard believed to be in his 50s, was found unconscious, fitting and had sustained an injury to his head.
“Ambulance staff immediately worked to assess and stabilise the man’s condition, administering drugs to help control his recurring fits before being immobilised onto a spinal board. An ambulance quickly transferred the man to the awaiting helicopter, which had landed in a nearby field, before being airlifted to Queen Elizabeth Hospital Birmingham.
"Medics at the hospital were pre alerted to the man’s arrival and serious condition.”
Officers can be reached on 101, quoting incident 18-s-270214.