Customers pinned down the suspect after Jodie Willsher, 30, was attacked at Aldi in Skipton on Thursday afternoon.
A 44-year-old local man was being questioned on suspicion of murder on Friday morning.
Mrs Willsher was married to husband Malcolm and their daughter is at primary school. She has not yet been formally identified by police.
He changed his profile picture on Facebook to show the couple smiling together.
The town council's mayor Andy Rankine said: "Skipton is a small but close-knit community where most people know each other. We are in shock about the sad events of yesterday where a store worker was murdered whilst going about her duties.
"The whole town is in shock and grieving over the loss of Jodie.
"Christmas this year will an ordeal for many residents."
People left tributes on a community Facebook page, saying "she was such a happy, friendly person", while another described her as a "bubbly, lovely girl".
One wrote: "Horrendous, so tragic for her family and for those who witnessed this barbaric act."
Another customer said she had seen Mrs Willsher earlier that day wearing a Christmas jumper at work.
One shopper who was in the store at the time of the attack said she had "never been so scared in my life".
The witness, who asked to remain anonymous, heard "loads of screams" then saw the victim lying on the floor and a man pinned down as "everyone screamed and ran up and down".
She said: "I just saw the aftermath. I was so scared I ran off. All the staff were racing about, not knowing what to do."
Floral tributes to Mrs Willsher have been left at the edge of the police cordon around the store, which is closed until further notice while police continue their investigation.
One man, who did not want to be named, lay down flowers describing the victim as an "absolutely lovely person".
He said: "I went to school with Jodie, primary school and high school.
"She was a well-liked person, I don't know anyone who had a grudge against her, she seemed, lovely, such a nice person.
"There's probably 20,000 people in Skipton and around 5,000 will know her, through school and working at the shop, it's that kind of small town.
"There's so many people she knew, so many people affected by it. It's shocking, an absolutely lovely person, never do any harm to nobody.
"She idolised her daughter. She put a snap on Facebook yesterday of her with her daughter cuddling in bed before she went to work.
"Nobody should ever go to work and not come home."
A sympathy card left with flowers read: "To our dear beautiful sweet friend. We are all broken. Sorry we never got our girls' night, here a glass to you. J xx"
Another card read: "Jodie, no words can explain how much you are going to be missed. You were truly 1 in a million. xxx L."
Earlier a team of police officers, plain-clothed detectives and scene of crime investigators opened the store and went inside, where half-filled shopping trolleys and items left at check-outs could be seen abandoned after the horror unfolded.
A steady stream of well-wishers came to leave flowers at the police cordon.
A cousin of the victim, who did not want to speak to reporters, arrived with flowers. She broke down in tears, clutching a bouquet of flowers, and sat on the ground, rocking back and forth and sobbing while being comforted by a man who was with her.
Kelly Blagden, 30, who also left a tribute, said she was a former school friend of Mrs Willsher, and they were both pregnant at the same time when her friend was expecting her daughter, Megan, now aged four.
She said Mrs Willsher had worked at the shop since it opened two years ago. She previously worked in a local Tesco store.
Mrs Blagden added: "She's a lovely girl, she was so in love, they were just the perfect relationship, they were so in love with each other and I just can't believe it really.
"We don't even know who did it. Nobody has said who it is.
"Still can't believe it really."