STOCKHOLM (AP) — A man who allegedly mapped military installations in Sweden was charged Wednesday with unauthorized possession of secret information.

Prosecutor Mats Ljungqvist said the 66 year-old man, who was not identified, had been gathering information for “a long time” and said it seemed that he had “a systematic approach” to mapping the installations, adding it appears “almost professional.”

“It involves a large number of facilities that are important for Sweden’s ability to defend the country in the event of war. The disclosure of information can mean but for the security of the kingdom,” Ljungqvist said in a statement.

Last year, two people had been charged with the same offense. A fourth person was convicted and sentenced to eight months in prison in December.

Sweden is in the brink of joining NATO. On Monday, Hungary’s parliament ratified Sweden’s bid to join the alliance, ending more than 18 months of delays that frustrated the bloc as it sought to expand in response to Russia’s war in Ukraine.