One of two men stabbed to death in Birmingham city centre may have been a Big Issue seller, police have said.
Officers said hundreds of people may have witnessed the stabbings in Union Street at about 17:50 GMT on Friday.
The first man was stabbed outside Sainsbury's and the second was found slumped outside Boots side entrance.
Minutes later, a 23-year-old man was arrested in New Street near to the Odeon cinema. He remains in police custody.
Post-mortem examinations on the two men, aged in their 30s, are due to take place later.
A spokeswoman for West Midlands Police said she was unable to confirm the identities of the two victims but said they had both "frequented the city centre" and that one may have been a Big Issue seller.
Union Street, which was closed on Friday night, has now reopened but some areas of the street and part of New Street remain cordoned off for forensic investigations to continue.
Police urged anyone who saw the stabbings - or the attacker fleeing the scene - to contact them.
A woman, who runs a stall near the Sainsbury's store and did not want to be named, said she believed both of the victims may have been homeless men.
She said: "If it's who I think it is they've been around here for a while.
"They were homeless and two lovely men. One of them had a dog called Scooby who I used to bring titbits for. I can't believe they're both dead."
Ambulance crews said police officers and members of the public had been helping give the stabbed men first aid when they arrived.
However, both went into cardiac arrest and died at the scene.
Supt Richard Moore, of West Midlands Police, said: "We can't assume anything at the moment, these are the very early stages of a major crime investigation.
"We will put all of our investigation resources into looking at the incident. What we can't do is jump to conclusions.
"It is a dreadful incident, but thankfully dreadful incidents like this are exceptionally rare."
West Midlands Police said extra police patrols would be out in the city centre over the weekend to reassure members of the public.