Couple killed in their Sydney burger bar

A couple killed inside their Sydney burger shop are being remembered by locals as community heroes with big smiles and infectious energy.

Police were called to the Buzzy Bee's burger shop on Oxford St in Cambridge Park, near Penrith in Sydney's west, after reports of an assault about 9.40am on Saturday.

The couple aged in their 60s were found with "significant injuries" after a member of the public alerted police.

A 31-year-old man has been charged with murder and was refused bail after being arrested at a home in Canley Heights about 12.30am on Sunday.

Police believe the victims and the accused were known to each other.

Flowers and tributes stacked up outside the closed roller doors of the restaurant on Monday, where devastated community members and friends left notes of mourning.

"I worked for you for both when my kids were at school and I will be forever grateful to have known two kind and genuine people," one letter wrote.

"You didn't deserve this ... (we) have lost two of the best."

Another said the pair were "pillars of the community", while multiple people referenced their big smiles.

A sign with a bee read "RIP Buzzy King + Queen" while another read "I will remember them".

Detective Superintendent Michael Cantrell said officers arrived to a "confronting scene".

"Obviously the welfare of our officers is being addressed, and we have systems in place for that," he told reporters in Sydney on Saturday.

Footage possibly relating to the incident has been posted on social media, Det Supt Cantrell said.

"I'm aware that there is footage around, and it's been through social media, and we're looking into that and looking at all lines of inquiry," he said.