One thing is clear from the thousands of pages of investigative files released Monday about the fatal shooting in 2012 of Cold Spring officer Thomas Decker: No one saw it coming. Not the parents and friends of the suspected killer, Eric J. Thomes, nor the behavioral psychologist who lived with him.

Thomes, 31, hanged himself in a shed after an hourslong standoff as police closed in to arrest him in the ambush-style shotgun slaying of Decker behind the Winners Sports Bar & Grill in Cold Spring two months earlier.

The investigative files revealed that Thomes had been fired that day from his job as a welder at Rotochopper Inc. in nearby St. Martin. He told police investigating Decker’s killing he was nowhere near the site of the killing that night.

Thomes said he was fired because he had missed work a couple of times without calling in sick. Others said his short temper also played a role, and that he had missed work because of court matters related to a 2011 drunken driving case. Decker had assisted in that arrest.

Transcripts from police interviews show that Thomes told investigators that he went to Corky’s Bar in Richmond right after he was fired and had several beers. He said he went home about 6:30 p.m., then went to Grumpy’s in Cold Spring, where he continued to drink and watch a football game. He said he went home about 10:30 p.m., then spent the night at a friend’s house. He later told police that he had lied, because he had spent the night with a woman and didn’t want his girlfriend to know.

The woman he identified as his lover, however, denied knowing anything about him.

His girlfriend, Sara Elaine Roberts, 42, told police that she was passed out on the couch from a night of drinking when Thomes arrived home that night about 10:30 p.m. She remembers that the local news was on. He stayed a short time, then headed back out again, she said. She told him not to come home if he drank too much.

Roberts is a licensed psychologist who works with children with autism. Investigators asked her about Thomes’ mood. She said he had been “down and depressed” since his ex-wife moved with their two young boys to Babbitt several months earlier but that he was feeling better because he learned that his boys were planning to move back soon.

The investigators asked her if Thomes ever talked about having a problem with any Cold Spring police officers.

“No. Matter of fact, he told me the night he got his DWI — well, I don’t know if it was Tommy [Decker] that gave it to him but I know that he said, ‘That officer could have taken me into Stearns County and locked me up’ but … the officer brought him back to the friend’s house, and he said that was really awesome.”

Thomes had numerous run-ins with police, all involving driving, starting when he was 16 years old. He was convicted in late 2011 for drunken driving in Cold Spring. He was then booked three times — in September, November and December — apparently in connection with the 2011 case, according to Stearns County jail records.

Decker assisted in the August 2011 arrest of Thomes. The arresting officer was Greg Reiter, a former part-time Cold Spring officer who was with Decker the night he was killed.

That night Reiter had gone to conduct a welfare check on Ryan Larson, a part-time bartender at Winners who reportedly had made suicidal comments to someone. Larson lived above the bar. Decker assisted, pulling his squad around back. He was shot after he got out of the vehicle.

Reiter told police that he was still in his vehicle when he heard two loud bangs, looked up and saw a large white male with a handgun pointed at him. He put the car in reverse and backed away as the shooter headed in the other direction, toward Decker.

Ryan was arrested but was released five days later without being charged.

About three weeks after Decker was killed, authorities released a transcript of the 911 calls. It revealed a caller reporting a dark van with a noisy exhaust system leaving the area. Thomes drove a green Dodge Caravan with a noisy muffler. Thomes and Decker, both of whom grew up in Cold Spring, graduated a year apart at Rocori High School — Thomes in 1999 and Decker the following year.

Decker’s death hit the small town hard, given that the father of four grew up there and had six years on the police force. More than 3,000 people attended his funeral.

Investigators found that Thomes — an avid hunter — had access to a friend’s 20-gauge shotgun that Bureau of Criminal Apprehension firearms experts determined “was likely” used to kill Decker. On Jan. 2, 2013, BCA agents and Stearns County Sheriff’s Office investigators went to arrest him. Thomes retreated to a shed behind his property and held them at bay for several hours. When authorities finally entered the building they found he had hanged himself with a tow strap. He had superficial cuts on his wrist. Nearby were a bloody knife, nine empty cans of Busch beer, a cellphone and two suicide notes.

“I’m sorry I can’t handle this anymore” one note said.

The other note told his boys that “dad loves you very much he was just messed up in the head. Be good boys.”

A couple of weeks later, Roberts told investigators that Thomes had been depressed because they worked opposite schedules and because he was losing touch with his sons. He said he needed treatment. Yet despite his difficulties, she said, he was well-liked.

“I mean, everybody who knew Eric loved Eric. And it was very obvious by his funeral. There were more than 350 people there who knew Eric, who loved him,” she said.