An arrest warrant was issued for a Bulgarian man three days before he allegedly stabbed and beheaded a UK woman in a Tenerife shop.
The BBC's Sarah Rainsford said a magistrate had ordered his arrest in connection with a violent attack.
Deyan Valentinov Deyanov, 28, was sent to a psychiatric unit following his arrest on suspicion of killing Jennifer Mills-Westley, 60, in Los Cristianos.
A local job office denied reports that she sought help before Friday's attack.
The denial, by the head of the job office, comes after media reports suggested Mrs Mills-Westley, originally from Norfolk, had sought refuge in the building minutes before she was killed.
Police spokeswoman Piedad Lozar told the BBC the Bulgarian man was arrested in January following an alleged assault in which he was said to have punched a man in the mouth and knocked his teeth out.
She said Mr Deyanov was admitted to a psychiatric unit for assessment the following month after residents complained about what they regarded as erratic behaviour.
He was later discharged but had to go to court every month to sign in with magistrates, as one of the bail conditions related to the alleged assault.
A detention order was issued on 10 May after he failed to appear at the court and it was received by the police two days after.
The spokeswoman said such orders "usually take several days to reach them".
As the order in this case did not come to the police marked as urgent, as some do, she said there was no reason for officers to believe he was dangerous.
The spokeswoman said: "This was not an urgent issue. There are more important things to deal with. We couldn't predict what would happen."
Police on the island have said Mr Deyanov had been arrested on two previous occasions - for criminal damage to property, and causing bodily injury.
One of Mrs Mills-Westley's two daughters, Sarah, said her mother had been "full of life, generous of heart and would do anything for anyone".
"We now have to find a way of living without her love and light and we would ask at this difficult time for some privacy as we try to come to terms with our loss," she said.
She said her mother was enjoying her retirement, travelling between Tenerife and France and visiting her other daughter in Norfolk.
Ms Mills-Westley retired to Tenerife after working as a road safety officer at Norfolk County Council.
Council leader Derrick Murphy said the news was "absolutely devastating" for those who used to work with her.
"We offer our sincere and deepest sympathies to Jenny's friends and family, in particularly her two daughters and five grandchildren," he said.
"As you can imagine, the terrible news obviously has come as a great shock to us. She was an incredibly well-respected member of the staff."
Ms Mills-Westley's former neighbour, Stella Watts, said she was a "kind, lovely lady" who used to take her to hospital to visit her sick partner.
Local officials have been analysing CCTV footage of the attack which shows a man walking into the supermarket - which sells Chinese food and tourist souvenirs.
Witnesses said the man attacked the woman without saying a word.
Local councillor Manuel Reveron said: "The man entered the shop and then cut this woman's neck and took the head in his hand outside."
"The woman died, unfortunately, because he was not well in the head. That's why this happened. I don't think there was any lack of vigilance by either the courts or the police," he added.
Following the attack, a security guard managed to wrestle the man to the ground, Mr Reveron said.
In a video posted on YouTube, Colin Kirby of Tenerifemagazine.com said security guards held down the suspect until the police arrived.
Christina Perez, a legal representative at a nearby court, said she and her colleagues ran indoors for safety.
"Everybody is shocked. It's a very safe area. You can usually go anywhere you want in the day or at night. This is really not normal."
Dominica Fernandez, of the Regional Interior Ministry, said the attack appeared to be random and that the suspect was well known in the area.
Regional newspaper La Opinion said the suspect had received treatment at the psychiatric unit of a local hospital in February after being involved in previous violent incidents.
The Mayor of Arona, Jose Alberto Gonzalez Reveron, said if Mr Deyanov had been in prison, this would not have happened.
"I would have liked to see the police react much sooner, to have prevented this murder, but I can't judge how they acted."
"This was a question of terrible bad luck. It could have happened to anyone."
The BBC's Maddy Savage said this kind of violence was extremely rare in the Canary Islands which attract more than 10 million tourists each year.
A Foreign Office spokesman said: "Consular officials in Tenerife are in contact with local authorities about this tragic incident and our condolences go out to the family at this difficult time."