One neighbour described the scene on Tuesday evening as "chaotic" after numerous emergency services descended on the usually peaceful farmland near Wray in the heart of the Forest of Bowland.
Police were called to a farm in the Moor Lane area at about 4.25pm on Tuesday following a report of a serious accident.
It was reported a Polaris Ranger vehicle pulling a trailer had fallen into the River Roeburn when a bridge collapsed.
Eleven people were in the ranger vehicle and trailer at the time of the incident.
Sadly, one man suffered fatal injuries and was pronounced dead at the scene.
A second man suffered a serious head injury and was taken to Royal Preston Hospital for treatment.
A third person suffered a serious back injury and was taken to the Royal Lancaster Infirmary, along with others suffering minor injuries.
Police say those in the vehicles were from a "shooting party" who were "travelling on private land" and were returning to a farm when the bridge suddenly gave way beneath them.
Emergency services attending the scene included North West Air Ambulance, North West Ambulance Service, Cave Rescue Organisation, Lancashire Police, Hornby, Bentham, Morecambe and Chorley from Lancashire Fire and Rescue and Kirkby Lonsdale from Cumbria Fire and Rescue.
"There were so many vehicles they didn't know where to park," a neighbouring farmer said. "I went to the farm and it was just chaotic. Everyone was in shock.
"The family are sound, it's a close community and I couldn't have survived up here without them.to be honest."
He added: "All the bridges have been there a long time. It's a beuatiful place but it can be wild out there too."
One visitor to the farm, which backs onto land leading to the river, said: "Emotions are running high; you can imagine what everyone is feeling right now. So many people have been affected, everyone is just in shock."
Another Roeburndale resident said everyone was praying for the best possible outcome for those injured.
"We saw the ambulances go rushing past," she said. "It's such an awful thing to happen, and hopefully everyone in hospital will be OK."
An investigation into the circumstances around the incident is now under way and the Health and Safety Executive has been informed.
Det Insp Kirsty Wyatt of Lancashire Police said: “My thoughts are very much with all those involved in what is a very sad and tragic incident.
“One man has sadly died and a number of people have suffered serious injuries.
“At this time we believe the vehicle was pulling the trailer, containing a number of people, when a bridge gave way. Those people were then thrown from the vehicle and trailer.
“Our investigation is at very early stages and enquiries are ongoing to establish what happened.”
A Lancashire Fire and Rescue Service spokesman said: "Five fire engines, including one from Cumbria and one from North Yorkshire, several special appliances and the air support unit attended initial reports of a road traffic collision on Moor Lane in Roeburndale.
"Firefighters assisted police, ambulance and mountain rescue teams in a multi-agency response to the incident which involved a vehicle pulling a trailer that had fallen into a river when a bridge collapsed.
"Several people were injured and sadly one person died. Our thoughts are with their loved ones at this difficult time."
A statement from the Cave Rescue Organisation said: "The team were called earlier today to attend an incident in Roeburndale alongside police, ambulance and fire crews.
"A sad outcome and our thoughts are with the family and friends of the deceased, and with others involved, or affected, by this tragic incident."
Coun Caroline Jackson, leader of Lancaster City Council, said: "We heard about this awful accident this morning and our hearts go out to all those involved and to their families and friends.
"Roeburndale is a wild and isolated spot even though it looks so close to Lancaster on the map.
"We are truly thankful that we have the air ambulance and mountain rescue services which were able to attend and support at speed."
Lancaster mayor Coun Mike Greenall said: "It is with deep sadness that we were to hear about the tragic accident in Roeburndale yesterday.
"Our heartfelt sympathy, thoughts and prayers are with all those affected at this difficult time."
Anyone with information which can help police can call 101 quoting log 0953 of January 18.