Dangling a $100,000 reward to jump-start tips from the public, investigators said Monday they are looking for any information about a black van with a loud exhaust system seen driving west down Main Street in Cold Spring the night police officer Thomas Decker was shot and killed.

Divers from the FBI and other agencies have also returned to the icy Sauk River that cuts through the central Minnesota town of 4,000 in hopes of recovering the .20-gauge shotgun police believe was the murder weapon when Decker died Nov. 29 behind a Main Street bowling alley and bar.

The six-figure reward, van search and divers' return were all signs that investigators seem no closer to cracking the mystery of who killed Decker than they were 20 days ago.

"This reward hopefully will generate leads and help find the person responsible for the killing of officer Tommy Decker," Cold Spring Police Chief Phil Jones said. "Right now, it feels like we all have a hole in our hearts that can't be filled, and finding the killer would start the healing."

The reward is believed to be the largest in Minnesota since up to $150,000 was offered when 11-year-old Kevin Brewer was fatally shot three times near a park in north Minneapolis in 2000. The new reward is being put forth by the nonprofit group Spotlight on Crime, a partnership of business leaders and law enforcement officials.

"We want someone to come forward with any piece of information that they have -- no matter how menial it may seem," Wade Setter, the superintendent of the state Bureau of Criminal Apprehension, said at a news conference.

Pursued 200 leads

Dozens of investigators, including FBI agents, have pursued 200 leads since Decker, 31, was shot twice in the head Nov. 29.

Ryan Larson, a part-time bartender studying industrial milling, remains a suspect, even though he was released five days after being arrested in his apartment above Winners bar about 100 yards from the parking lot were Decker died.

"Nobody has been ruled out of this investigation at this time," BCA assistant superintendent Drew Evans said.

Part-time officer Greg Reiter, who heard two loud bangs from his nearby squad car, remains on paid administrative leave, which is standard in such cases. He has been cooperative and has spoken to investigators several times, Evans said.

Documents say Reiter put his squad car in reverse, heading east out of the parking lot as a suspect walked off to the west. Reiter reported seeing a handgun, but authorities continue to say they believe a shotgun killed Decker.

"I wouldn't characterize it as sawed-off or non-sawed off," Evans said. "But evidence at the crime scene leads us to believe a .20-gauge shotgun was involved in the actual killing."

Authorities declined to discuss specific details, but asked about the discrepancy of Reiter's account of a handgun and the shotgun evidence, Evans said the case is "dynamic and the facts will continue to change as we fully investigate."

Stearns County Sheriff John Sanner said police officers take an oath to protect and serve, and when one is killed "discharging those duties, we're all left feeling a little bit more vulnerable.

"The bottom line is this is a cold-blooded killing and the sooner we get this individual that's responsible for this behind bars, the better all of us will sleep at night."

Curt Brown • 612-673-4767