Jordan Gatley left the British Army in March "to continue his career as a soldier in other areas," Sky News reports.
A former British soldier has died fighting Russian forces in the Ukrainian city of Severodonetsk, his family have said.
Jordan Gatley left the British Army in March "to continue his career as a soldier in other areas," Sky News reports.
Gatley flew to Ukraine soon after he left the British Army to help fend off Russian forces and train Ukrainian soldiers.
Announcing the news on Facebook, his father Dean wrote: "Yesterday (10/06/22) we received the devastating news that our son, Jordan, has been shot and killed in the city of Severodonetsk, Ukraine."
Dean added: "His team say they all loved him, as did we, and he made a massive difference to many peoples lives, not only soldiering, but also by training the Ukrainian forces.
"Jordan and his team were so proud of the work they were doing and he often told me that the missions they were going on were dangerous, but necessary.
"He loved his job and we are so proud of him. He truly was a hero and will forever be in our hearts."
Mr Gatley's post, written late on Saturday, has hundreds of condolence messages.
His son is the second Briton to have been confirmed dead in Ukraine during the war.
The first British casualty, Scott Sibley, 36, died in late April and was also a former member of the British Armed forces.
The city of Severodonetsk has become the main focus of the Russian offensive in recent weeks.
It is one of the last areas in the occupied eastern Luhansk region that is still under Ukrainian control.
On Sunday, the Ministry of Defence (MoD) posted in its latest intelligence update that "Russia is using its overmatch in force ratio and artillery to gradually seize territory in and around Severodonetsk".