A man detained but never charged in the murder of a Cold Spring police officer is suing Sauk Rapids Police Sgt. Tom Roy for defamation, claiming the officer wrote on a Facebook page that he was likely the killer or a participant in the crime.

Cold Spring officer Thomas Decker was shot in the head outside a bar on Nov. 29, 2012, shortly after making a welfare check on Ryan Larson. The check was prompted by a call from Larson’s mother, who expressed worry that her son was suicidal.

Larson was taken to jail but was never charged with a crime, and released five days after the shooting. Another man, Eric J. Thomes, was later named a person of interest in the murder but killed himself after a standoff with police a month later.

The suit Larson filed in Benton County last week claims that Roy posted comments on a Facebook saying Larson was “far from innocent in this case. We could not and would not have held you in custody for four days without some ‘reasonable suspicion.’ Search your soul and do the right thing in this, be honest and tell all you know. … You … are likely the killer or a participating witness.”

The suit said that Roy’s statements wrongly created the impression that he had “engaged in illegal, immoral, criminal or wrongful conduct.” Larson is seeking damages of at least $50,000.

Larson already settled defamation suits with KSTP and WCCO for undisclosed amounts last year.

A hearing is set for April 2.