Authorities announced Tuesday that they have concluded that a man who committed suicide in January after he fell under suspicion in Cold Spring police officer Tom Decker's death was Decker's killer.

But they don't know why.

The 31-year-old police officer was ambushed with a shotgun as he responded to a call on the night of Nov. 29, 2012, and left to die behind a downtown Cold Spring bar. By saying that Eric Thomes would have been arrested in Decker's slaying had he lived, authorities wrapped up the active portion of an eight-month investigation.

But "what was the motive, and did the shooter act alone?" Stearns County Sheriff John Sanner said Tuesday. "Those are the questions still hanging out there that we would like to get the answers to ourselves."

Those unanswered questions explain in part why it took investigators the better part of a year to finally name Thomes — long considered a "person of interest" — a suspect in Decker's killing.

Tuesday's announcement by the Minnesota Bureau of Criminal Apprehension also for the first time cleared the name of Ryan Michael Larson, 34, who was arrested and jailed for five days, but never charged in Decker's death. The BCA has now handed over its duties to the Sheriff's Office.

Thomes

Cold Spring Mayor Doug Schmitz said the latest developments will offer some limited relief to the central Minnesota town of 4,000.

"I think it's going to bring some closure to some people," he said. "The evidence was leaning so that they would have made an arrest with Thomes."

Schmitz said that doesn't mean Thomes would have been convicted, "but they would have arrested him" had he not taken his own life.

However, "there are a lot of unanswered questions that probably never will be answered, because he took a lot of the answers to his grave," Schmitz said.

Thomes, 31, a divorced father of two boys, hanged himself Jan. 2 in a metal outbuilding in rural Cold Spring after being questioned by authorities. He ran into the building when he saw investigators arrive for another interview. Authorities said last January that they found the shotgun used to kill Decker on a property to which Thomes had access, but stopped short of declaring he was the person who killed Decker.

Thomes grew up in Cold Spring and graduated from Rocori High School in 1999, a year before Decker. He was a regular patron of Winners Bar, near where Decker was shot, and facing imminent arrest after he failed to appear in court in connection with a drunken-driving charge. He was later linked to a vehicle seen leaving the bar after Decker was shot, and police had interrogated him several times before he committed suicide.

Thomes' parents, who live in Cold Spring, did not respond to a request for comment. Alicia Decker, the officer's widow, did not want to comment, according to her attorney, Claudia Revermann.

Initial suspect cleared

Cold Spring's interim police chief, Chris Boucher, who worked with Decker for six years, said Tuesday's developments bring no closure to the department.

"We still have a lot of questions that we don't have answered," said Boucher, who replaced longtime Chief Phil Jones when he resigned last month.

Why Thomes would have killed Decker and whether he acted alone in the alley remain unknown, Boucher said.

Because investigators haven't said who else was in the alley, Boucher thinks Larson remains in the mix, despite the BCA statement that said, "At this time, the investigation has provided no information that Mr. Larson participated in Officer Decker's murder."

Said Boucher: "There again, we don't know who was all there that night, do we? So it doesn't really clear Larson to that extent."

However, BCA spokeswoman Jill Oliveira was more specific in clearing Larson.

"At this point, we believe there is no information that he participated in Officer Decker's murder," she said. "Although there is a past connection between the suspect and Mr. Larson, there is no connection we determined that was related to the crime."

Larson did not respond to messages seeking comment. After his release, he gave multiple interviews declaring his innocence and said he was never suicidal the night Decker and part-time officer Greg Reiter responded to a welfare check at his apartment above the bar after his concerned family called police. Reiter has since left the department.

Murder weapon identified

Boucher said that one thing now cleared up for him is that the murder weapon was indeed a shotgun found in Thomes' possession.

Larson

"Obviously they recovered the shotgun that was used that night," the interim chief said. "We're not looking for that gun anymore; that's resolved."

Sanner said much of the investigation involved DNA and other laboratory testing, as well as pursuing tips from potential witnesses from the night of Decker's death.

Anyone with additional information related to the shooting or Thomes' actions around that time is urged to call the Stearns County Sheriff's Office at 877-782-5683 or the BCA at 877-996-6222.

curt.brown@startribune.com 612-673-4767 abby.simons@startribune.com 612-673-4921