Two men have died after being stabbed, in two unrelated incidents, in north-west London and Somerset.
Scotland Yard said London officers were called to reports of an injured man at an address in Marsh Road, Pinner, at around 6am on Sunday. It is believed he was opening a newsagents, Marsh Food and Wine, at the time of the stabbing.
The victim was pronounced dead around 45 minutes after the incident. The Metropolitan Police said enquiries were under way to identify the man and his next of kin.
Detective Chief Inspector Simon Stancombe said: "I am appealing to anyone who was in the area around Marsh Lane this morning and saw anything of interest to contact police.
"This was a violent robbery that has escalated, resulting in the murder of a man.
"It appears the till was stolen from the shop during this robbery and this may have been discarded by the suspect. If you have come across this, we want to hear from you.
"I am particularly keen to hear from anyone who saw a black Vauxhall Astra that was driven away at speed south down Cecil Park immediately after the attack.
"We think that car was parked in Cecil Park prior to the murder - if you saw this, or have any other information that could help us progress this investigation, I would urge you to get in contact."
A large section of Marsh Road has been cordoned off, and police forensics tent has been erected in Marsh Road outside a Costa Coffee and an off-licence.
One resident described Pinner as "lovely", but said she was not shocked by the news as such incidents are "happening in all areas".
Mary MacNamara, who has lived in the area for four years, said: "We all see what's going on generally and it (such crime) seems to be happening in all areas.
"It's happening every day. Nobody does anything about it."
She said the Government is too focused on Brexit and should be looking more closely at the causes of violent crime.
"The Government are doing nothing about it," she said before adding: All they do is fight about Brexit."
In Somerset, eight people have been arrested after a man died from knife wounds, police have said.
Avon and Somerset Police have launched a murder investigation following the death of the man, aged in his 30s.
The force received a report of a disturbance at a property on Merlin Drive in Wells, Somerset, involving a number of people at 4.25pm on Saturday.
Officers attended the scene and found two men with knife wounds on nearby Wookey Hole Road.
One of the men died of his injuries at the scene and his next of kin have been informed.
The injuries sustained by the other man, also in his 30s, are not life threatening or life changing but he remains in hospital for medical treatment.A force spokesman said: "Armed officers were deployed to the scene ... The police helicopter was also used in the operation.
"In total, six men and two women, all from the Somerset area, were detained in connection with the incident and currently remain in police custody."
A post-mortem examination of the man who died and formal identification will be arranged "in due course", he said.
Specially trained officers will be providing support to the man's family.
Detective Inspector Alistair Hammett, senior investigating officer, said a full investigation was being carried out into the "very tragic incident".
"I appreciate this incident will shock local residents and we are increasing patrols in the area to provide reassurance," he said.
"At this stage, we believe this to be an isolated incident involving people known to each other."
A murder investigation has been launched and police are asking anyone with information to call 101 or Crimestoppers anonymously on 0800 555111