Detective Inspector Paul Shortt, of Nottinghamshire Police, said: "This was a shocking incident that will have caused considerable alarm to anyone who witnessed it.
In an earlier statement, Detective Inspector Shortt said: "This was an appalling act of violence carried out in full view of members of the public.
A 16-year-old boy has been arrested after another teenager, 17, was stabbed in front of shoppers in a Primark store in Nottingham city centre.
"Our thoughts are with the victim and we are focused on supporting our colleagues who were in store at the time," a statement said.
The victim suffered a stab wound to the chest after he was attacked inside the shop in Long Row at about 11.30am on Sunday.
