Inside, police found documentation indicating Thompson considers himself a sovereign citizen, a group of people who do not recognize federal law, US currency or taxation. They are considered domestic terrorists by the FBI.
Records show Thompson has previous convictions for assault and robbery.
At an arraignment on Tuesday, he was held in lieu of $2 million bail, and is due to appear in court again on August 18.
The victim's cousin Jim Banks told the Courant that King, who won a national bridge championship in 2016, was a kind and gentle person who "would never hurt a soul."