Shortly after 9am on Saturday, Boris Johnson and Keir Starmer bent to lay wreaths and, united briefly by grief, turned grimly from the Essex church where Conservative MP David Amess had been killed less than 24 hours earlier.

Accompanied by the rumble of helicopters, the political leaders soon left Leigh-on-Sea and a community searching for answers.

What made someone kill one of Westminster’s most admired MPs in a town judged one of the country’s best places to live? Who is the 25-year-old still being questioned on suspicion of the MP’s murder? Did Amess know him?

Counter-terrorism detectives from the Met’s SO15 unit are investigating the killing. So far, the Metropolitan Police’s counter-terrorism command has referred only to “a potential motivation linked to Islamist extremism”.

Reports indicate the suspect, said to be a British national of Somali heritage, is not on MI5’s vast, evolving database of people of interest. However, he is believed to have been referred to the Prevent programme. Police have said they are not looking for anyone else.

Whatever emerges from the investigation, the events soon after noon on Friday have traumatised the people of Leigh-on-Sea and far beyond.

Previous Islamist terrorist attacks have prompted a rise in hate crimes, and the police declaration of a terrorist incident has already turned attention to Leigh’s modest Muslim population, which, according to the last census, stood at 1.9% for Southend-on-Sea, which incorporates Leigh and Belfairs, the district where Amess was stabbed to death at a constituency surgery.

The Zaidis are one of the area’s most prominent Muslim families and were close friends with Amess. The death of Habib Zaidi, 76, who ran a Belfairs GP surgery before succumbing to Covid-19 last year, was mentioned by Amess in parliament.

Their relationship, said Zaidi’s wife, articulated what she believed was the effortless multiculturalism of Leigh-on-Sea. Speaking 100 metres from where Amess was killed, she said: “It’s extremely integrated around here. There’s no race hate, everyone coexists here in peace.” Her son shook his head when asked if the MP’s death could destabilise the area.

Further along Eastwood Road North, student Grisharni Raviraj also described a town where she had experienced no racial disharmony.

However, she admitted that already her parents had discussed security concerns in the wake of the tragedy, despite the family not being Muslim. “My parents have warned me, saying the first thing people notice is the colour of my skin,” said Raviraj, who has lived in the area for a decade.

Across the road, Obinna said she was convinced that the perpetrator was not local. “This act must have been imported. There is no way this person can be from around here,” she said, gesturing towards the police tape keeping the public from the scene of Amess’s death.

To demonstrate the district’s safety she said she lived around the corner from the Belfairs Methodist church, where the stabbing took place. “Last night, even after what happened, I left my back door open all night,” added Obinna, who has lived in the area for more than 20 years.

Meanwhile, a joint statement from all of Southend’s mosques described the fatal stabbing as an “indefensible atrocity”. Published on the Essex Jamme Masjid website, it said: “We look forward to the perpetrator being brought to justice.”

Local resident Bhawani Bhardwaj, 74, echoed such sentiments. Stressing that the local south Asian community was “peace-loving”, he said: “If you read the Qu’ran, it says clearly that there shouldn’t be any violence.”

He added: “This is the first time something like this has happened in Southend and we’re all really disturbed.”

Meanwhile more details emerged of the horrific moments Amess was allegedly attacked by a man waiting in the queue of constituents during his fortnightly surgery.

Southend councillor John Lamb, another close friend of Amess, said the attacker was waiting to see the MP then “drew a knife and stabbed him” when he was summoned.

Butcher Lee Jordo, who works in the bustling parade of shops 100 metres from the scene, described hearing a commotion on Friday afternoon.

He rushed over, arriving 15 minutes after the attack began, and saw a woman screaming on the phone: “Get here quick, he’s not breathing.”

Unsurprisingly, he said the town was awash with rumour about how the attack progressed and the killer’s motives. “People have said the guy who did it didn’t make any attempt to run off. [Amess] was stabbed 17 times and then the guy just sat there,” said Jordo.

“It could have been a lot worse,” he said. “I dread to think what would have happened if he’d have gone on a rampage.”

He, too, is among those who hope that the quest for answers doesn’t motivate some to target the town’s small south Asian population. “We can’t allow this to scare and divide people.”

Others wondered how Amess’s two female members of staff – alongside him during the attack – were coping. Jane Riddle, who has lived in Belfairs for more than 50 years, said a neighbour was one of the assistants.

“She’s worked for David for years. I think she’s got a good support network and she’s a governor at a local school, but it must be awful,” she said.

As the police investigation continued into the night and the pile of flowers outside the church steadily grew, crowds congregated to pay tribute to their former MP.

James Duddridge, MP for the neighbouring constituency, addressed the gathering with a microphone, describing how he had been inundated with tributes to Amess and reassured local people that “there is no ongoing threat to Southend”.

Later, Stephen Aylen, a former independent councillor for the area, said that the death of “the perfect local MP” had prompted him to reanalyse some of the behaviour he had experienced as a politician.

“I’m a nothing but I’ve been pushed up against the wall and punched. I’ve had human shit thrown at me … people are nasty but to pull out a knife is so exceptional,” he said.

Yet most of those interviewed by the Observer portrayed Leigh-on-Sea as a place where extreme violence was rare. Many mentioned the murder of a teenager in Old Leigh in February as the only incident they could recall before the bloodshed in Belfairs on Friday afternoon.

No longer. From here onwards, their town will be synonymous with the killing of its much-loved MP.