The city of Nottingham has been shaken by a series of attacks which left two teenage students and another man dead.
Barnaby Webber, 19, Grace Kumar, 19, and a man in his 50s were fatally stabbed. Three people were hit by a van police believe was stolen from the older stabbing victim.
A suspect was Tasered by police before being arrested on suspicion of murder.
Counter-terrorism police are involved in the investigation, but no link to extremism has been confirmed.
Police said they were still in the early stages of the inquiry into the attacks, which occurred during the early hours of Tuesday, and had yet to determine an exact motive.
The suspect, 31, is believed to be a migrant of West African origin.
Reporting from the scene, the BBC's Daniel Sandford says he understands the suspect has a history of mental health issues.
That is why at this stage, while counter-terrorism police are assisting the investigation, they are not running it, he adds.
Several roads in Nottingham were closed throughout the day as police combed for evidence, and armed officers were seen on the city's streets.
Nottingham City Council leader David Mellen said the city was in "shock and mourning", while the city's three MPs said the area had been "devastated" by the bloodshed.
Police have not formally identified the victims, but Mr Webber, a student at Nottingham University, was named by friends and family.
The amateur cricketer from Taunton was described by Somerset's Bishops Hull Cricket Club as a dear friend whose memory would live on.
A tribute continued: "'Webbs' joined the club back in 2021 and has since then been a key part of our club and made such an impact in such a short space of time."
Grace Kumar - who is also known as Grace O'Malley-Kumar - has been named locally as the second victim and is said to be a talented hockey player. The man in his 50s has also not been named by the authorities.
England Hockey said it was "deeply saddened" by Ms Kumar's death.
"Grace was a popular member of the England U16 and U18 squads and our thoughts are with Grace's family, friends, teammates and the whole hockey community at this time," it said.
The deadly episode unfolded in less than two hours.
Police were called out to Ilkeston Road around 04:00 BST where they found the two students fatally injured.
Some time after 05:00 the body of the man whose van was apparently stolen was found with knife wounds in Magdala Road, just under two miles (3.2 km) from the scene of the first two killings.
Around 05:30 the van was driven into three people waiting at a bus stop on Milton Street in the city centre. One of those hit remains in hospital fighting for their life. The other two were lucky to escape with minor injuries.
Shortly after the van attack the vehicle was stopped in nearby Maples Street and the suspect was detained after being Tasered.
In the afternoon armed officers carried out a raid on a property on Ilkeston Road.
Nottinghamshire Police, which described the incident as "horrific and tragic", said detectives were not looking for anyone else in connection with the inquiry.
Cllr Mellen told BBC Breakfast it had been an awful day for the city but the "spirit of Nottingham will shine through this".
"It was shown right at the start of this as people ran to help those who had been driven into as they were waiting for a bus first thing in the morning," he said.
One eyewitness told the BBC he had seen a young man and young woman being stabbed in Ilkeston Road, close to the junction with Bright Street.
The man, who asked to remain anonymous, said he had heard "awful, blood-curdling screams" and had seen a man dressed in black, with a hood and rucksack, "grappling with some people".
"It was a girl, and a man or boy she was with - they looked quite young," he said.
"She was screaming 'Help!'. I just wish I'd shouted something out of the window to unnerve the assailant.
"I saw him stab the lad first and then the woman. It was repeated stabbing - four or five times. The lad collapsed in the middle of the road.
"The girl stumbled towards a house and didn't move. The next minute she had disappeared down the side of a house, and that's where they found her."
The attack has sent shockwaves through Nottingham's large student population, a city which is home to two universities and more than 50,000 students.
A male student, who knew one of the victims, said: "It hurts, it hurts a lot. It's the first time I'm dealing with something like this and at university it's a challenge for sure.
"The road that I live on leads directly on to the scene of the incident - when it happens on your doorstep you feel scared and frightened.
"It makes you realise what's important in life, to check on people and see how they're doing."
- If you have been affected by any of the issues raised in this story you can visit BBC Action Line.
The University of Nottingham confirmed "with great sadness" that the two teenage victims of the attack had been students there.
A planned graduation event was cancelled on Tuesday, and its students' union said it was "devastated and shocked" by the attacks.
Neighbouring Nottingham Trent University said it had contacted its students to reassure them and encourage them to speak to staff about safety concerns.
Ahead of a church vigil held in the city on Tuesday evening, Paul Williams - the Bishop of Southwell and Nottingham - said the city was "in shock".
"But what people in Nottingham do is pull together, friendship is the heart of Nottingham," he said.
Prime Minister Rishi Sunak said: "My thoughts are with those injured, and the family and loved ones of those who have lost their lives."
Home Secretary Suella Braverman said her thoughts were first and foremost with "all of those who've been involved, their friends, their families and their communities".
She urged anyone with any information relating to the incident to report it to the police, who she says should be allowed "time and space" to investigate.
Labour leader Sir Keir Starmer sent his "thoughts to all those affected and to the emergency services who are responding".