A firefighter died after being hit by a car as he tackled a fire in another vehicle on a motorway.
Paul Mallaghan, 46, was putting out the fire in a Saab car on the A1 (M), in Hertfordshire, when the crash happened.
He was fatally injured when the Saab was struck by a VW Golf, between J7 and J8 near Stevenage, on Saturday night.
Mr Mallaghan, who was based at Stevenage fire station, died later in hospital. Another firefighter was also taken to hospital with injuries.
The cause of the incident and the exact circumstances surrounding it are being investigated, Hertfordshire Police said.
The driver of the Golf car was also treated in hospital.
Chief Fire Officer Roy Wilsher said: "This is an absolute tragedy and we are completely devastated. Our thoughts and sympathies are with Paul's family at this very sad time."
Mr Mallaghan was from the same Blue Watch in Stevenage where two firefighters died in February 2005 in a fire at a flat.
Tony Smith, brigade secretary for the Fire Brigades Union in Hertfordshire, said: "The brigade and the watch were just starting to get over the loss of firefighters Jeff Wornham and Mike Miller.
"To lose three fire-fighters from the same watch at two separate incidents is cruel beyond imagination."