Matthew Trickett, 37, lived in the town of Maidenhead, west of the capital London. Trickett was found dead in Grenfell Park in the same town on Sunday.
Thames Valley regional police announced that the cause of Trickett's death could be determined after an autopsy.
Trickett received emergency treatment when he was found but was pronounced dead at the scene.
Authorities urged people who were in the park on Sunday to contact police if they had any information.
"We are grieving the loss of our beloved son, brother and family member Matthew," Trickett's family said in a statement, asking for respect for the privacy of Matthew Trickett, who lost his life.
He served as a soldier in the British Royal Navy for six years
Trickett, an immigration officer at the Home Office, served as a soldier in the British Royal Navy for six years between 2007 and 2013.
Trickett also owns a private security firm called MTR Consulting.
Last week, Trickett, along with Chi Leung Wai and Chung Biu Yuen, appeared in court under the National Security Law and were charged with assisting Hong Kong intelligence.
They were accused of gathering information "useful to foreign intelligence services" and conducting surveillance between December 20, 2023 and May 2, 2024.
The suspects were alleged to have "spied on pro-democracy dissidents" in the UK for the benefit of Hong Kong intelligence.
They were also charged with "breaking and entering" an address in the UK on May 1.
