Three people have been found dead in Nottingham, with a 31-year-old man arrested by detectives.
Two of those who died were discovered in the street on a road to the west of the city centre.
The other body was found to the north.
Another three are in hospital after a van tried to run them over in what officers think was a connected incident.
Former Metropolitan Police detective Graham Wettone says responders will be trained for this.
"It sounds like they've encountered that horrific incident, and then a second incident and possibly even a third incident.
"It was a traumatic night for everyone involved in it, everyone that has witnessed it or that's been part of it.
"We're looking at some potential hours before we get any potential indication of what's happened here."
