A village in northwestern France where a Dutch retiree allegedly shot dead an 11-year-old British girl and gravely wounded her two parents was in shock Monday over the "abominable" violence.

"It's a tragedy," said Kim McKanney, 64, a British pensioner out with her poodle a few hundred metres from the scene of the crime.

"I'm shocked and upset that a family has been affected like this and a child killed in a little village which is so quiet, peaceful and friendly," she added, looking close to tears although she did not know the victims.

"You might expect it in a city but not here."

Sitting in the Monts d'Aree hills in western Brittany, the isolated hamlet of Plonevez-du-Faou had been home to the British family since 2019.

The father, Adrien T, began clearing vegetation and detritus from his land, formerly the site of a sawmill - drawing the ire of the neighbouring couple aged 70 and 69 known locally as "the Belgians", although prosecutors say they had Dutch nationality.

With the neighbours bothered by the noise of Adrien's chainsaw and by the fact their house was now visible from the road, the town hall initially stepped in to mediate.

"We could see (the neighbour) was griping but there wasn't anything at all alarming" about the dispute, mayor Marguerite Bleuzen said.

"It was (Adrien's) land, he can do what he likes with it."

'Completely wild-looking'

Aside from the friction with their neighbours, the British family quickly put down roots in their village, sending their daughters to nearby schools.

Described as "a lovely person", the mother worked as a home carer for elderly people.

The family also helped organise village parties, even allowing visitors to park on their land.

"They're very nice, very kind, always happy to help," said a close neighbour in his 80s who asked not to be named.

He drew a contrast between the family and the suspected shooter, who he said he had "never seen face-to-face" since the couple arrived in 2017.

"We never saw them. No contact, nothing at all," added the elderly man, who said that "nothing has ever happened here" in all the years since he arrived in 1948.

"No one knew" the suspect, agreed mayor Bleuzen, who described his appearance when arrested as "a little guy with long white hair, a long beard, and completely wild-looking".

"What on earth could have been going on in his head?" she wondered.

Saturday's multiple shootings were "appalling, abominable," said one local resident as she left white roses on the threshold of the British family's home.

The slain girl "was the same age as my grandson, I'm really moved. Who wouldn't be?" she added, herself appearing close to tears.

A source close to the investigation told AFP that a large amount of cannabis had been found in the suspect's home when it was searched by police.

Prosecutors from nearby city Brest will hold a press conference later Monday.