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Authorities in northern Illinois are combing through hundreds of leads on social media and surveillance video and continuing to canvass door to door in pursuit of three suspects wanted in a fatal police shooting.

The manhunt in Fox Lake, a village on the Wisconsin border, has been hampered by a vague description of the suspects — two white men and one black man — given by the officer before he was slain Tuesday morning.

"Not going to set a time limit on this (search)," George Filenko, chief of the Lake County Major Crimes Task Force, said at a news conference Wednesday. "I have a murdered colleague — a police officer — and we’re not going to stop."

Read more at NBC Chicago

Police refused to give further details about the investigation, and would not confirm reports that Lt. Charles Joseph Gliniewicz's gun was recovered at the scene where his body was found. Police initially said his weapon and pepper spray were missing.

Filenko did provide a general scenario about the circumstances surrounding Gliniewicz's death. He said the suspects were in an area of open fields and abandoned businesses, and the veteran officer apparently saw the men and stopped to question them at 7:52 a.m. local time.

PHOTOS: Massive Manhunt Targets Suspects in Illinois Cop Killing

Gliniewicz did radio for backup about three minutes later, but by the time other officers arrived, he was found dead on scene at 8:09 a.m., police said. In less than 15 minutes, the suspects were able to vanish.

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Filenko said an autopsy was conducted of Gliniewicz on Tuesday night, but declined to release details.

He continued to urge the public for help: "Homicides are greatly assisted by public information, and all it takes is one tip or good lead to break a case wide open."

Fox Lake Lt. Charles Joseph Gliniewicz. Lake County Sheriff’s Office

Several school districts in the Fox Lake area cancelled classes and residents were warned to stay on high alert. The search area broadened Wednesday morning after units focused the day before on an immediate 2-square-mile area over 14 hours.

Helicopters were deployed to scan the terrain of marshlands and dense woods that make up Fox Lake, home to about 10,000 people and about 60 miles north of Chicago. Hundreds of officers toting high-powered rifles and binoculars were joined by federal agents and more than 45 police dogs, authorities said.

The search, however, has not expanded into neighboring Wisconsin, Filenko said.

"We’re looking for suspicious activity, we’re looking for the offenders and we want to let the Fox Lake community to know they’re safe and we’re keeping an eye out for them as well," Lake County Sheriff's Office spokesman Det. Christopher Covelli told reporters Wednesday morning.

Illinois State Police said several teams, including SWAT and air operations, were helping in the manhunt Tuesday night. The federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the FBI were continuing to assist.

In and around Fox Lake, residents were asked to stay indoors. Police have even taken people's dogs outside to relieve themselves rather than let residents do it themselves, The Associated Press reported.

Fox Lake Mayor Donny Schmit said Gliniewicz, a military veteran, was known fondly as "G.I. Joe."

"Today, not only did Fox Lake lose a family member — I lost a really dear friend," Schmit said at a news conference Tuesday.

Our thoughts & prayers to the family, friends, fellow officers of our fallen brother Lt. Joseph Gliniewicz #FoxLake pic.twitter.com/7hwVay1UAT — Tom Ahern (@TomAhernPIO) September 2, 2015

Vigils are planned Wednesday night for Gliniewicz, who was set to retire from the Fox Lake Police Department last month but stayed on a while longer as a favor, NBC Chicago reported.

Gliniewicz had an enthusiasm for and dedication to law enforcement, those who knew him said. His work included guiding children as part of a local Police Explorers unit.

"He would always try to help everybody," youth member Thomas Ashbacher told NBC Chicago. "He would give his shirt off his back if he could."

Illinois State Rep. Barbara Wheeler asked the community for prayers. "Fox Lake lost a true hero today," she said.

Congressman Robert Dold called Gliniewicz's death a "heartbreaking reminder of the sacrifices made every day by those who have dedicated their lives to protect us."

"Today the Fraternal Order of Police lost a fellow member and brother who died heroically serving his community," Illinois Fraternal Order of Police President Chris Southwood said in a statement to NBC Chicago.

"Our thoughts and prayers go out to the slain officer's family, friends and fellow police officers," Southwood said. "He leaves a legacy of several decades of service to Fox Lake for which we are humbly grateful."