He married Gustaviana Elisabet Löwen (1764-1844) in 1783, and had two daughters and two sons: Gustafva Eleonora Löwenström (1785-1860), Carolina Lovisa, Johan Jacob and Carl David.

Although he was acquitted due to lack of evidence, he later maintained in his confession that this incident sparked his fire of hatred towards the king, fuelled by the contemporary revolutionary movement in Europe.

Beginning in 1788 the Swedish nobles were starting to become violently opposed to the king, who, through the aid of the other estates in Parliament, had wrested most of their power from them and was now ruling the nation as an absolute ruler.

[1] This dislike was increased by a war against Russia and his implementation of the Union and Security Act of 1789 which stripped the nobles of nearly all of their power and privileges, as well as by the king's desire to interfere in favor of Louis XVIII in the ongoing French Revolution.

[1] Anckarström, a man of strong passions and known to have a violent temper, decided the only path forward was the assassination of the king and communicated his intention to other disaffected nobles, including the Counts Claes Horn and Adolf Ribbing.

[1] On 16 March 1792, Gustav III had returned to Stockholm, after spending the day at Haga Palace outside the city, to dine and visit a masquerade ball at the Royal Opera.

[1] After dining, the king with Baron Hans Henrik von Essen at his right arm went around the theatre once and then into the foyer where they met Captain Carl Fredrik Pollet.

Anckarström stood at the entrance to the corridor and edged himself behind the king, took out a pistol from his left inner pocket and either he or Count Ribbing, who was next to him, pulled the trigger.

Curiously, the murder had been predicted to the king four years earlier, when he paid an anonymous visit to the celebrated medium of the Gustavian era, Ulrica Arfvidsson.

Anckarström is a character in Daniel Auber's opera Gustave III and Giuseppe Verdi's Un ballo in maschera (A Masked Ball).