Illinois police are appealing to the public for help as they widen the perimeter in the search for three suspects linked to the killing of a 30-year veteran officer, but there are few specifics as to who exactly authorities are searching for as the manhunt enters its second day.

Two white males and one black male have been identified as suspects in the death of Lt. Charles Joseph “Joe” Gliniewicz, 52, on Tuesday morning. 

Gliniewicz, 52, was shot at approximately 8 a.m. local time Tuesday after he radioed in to tell dispatchers he was chasing three men on foot in Fox Lake. Communication with him was lost soon after. Colleagues who responded found Gliniewicz shot in a marshy area near U.S. Highway 12, a main road through the village of about 10,000 people near the Wisconsin border and about 55 miles northwest of Chicago. He was pronounced dead at the scene.

“Residents need to keep a watchful eye and report any suspicious activity"

- Det. Christopher Covelli

Police on Wednesday didn’t provide further information.

“Residents need to keep a watchful eye and report any suspicious activity,” Detective Christopher Covelli said. “Anything out of the ordinary. The public can help. If they see something unusual, report it.”

Covelli said cops had widened their original search area and were engaging in “saturation patrols.”

“We’re gonna continue to be out there, continue to work very hard, work with the community,” Covelli said.

Overnight, helicopters aided about 100 officers who searched the area, a sheriff's office spokesman said. Meanwhile, several schools in the area announced that they would be closed Wednesday due to the ongoing manhunt.

As the search continued, dozens gathered for hours along a street in the village to show their support for law enforcement officers.

An emotional Fox Lake Mayor Donny Schmit described the murdered officer as a personal friend, a three-decade member of the department and a father of four sons.

"We lost a family member," Schmit said of the officer known around town as "GI Joe." ''His commitment to the people of this community has been unmatched and will be dearly missed."

"This particular officer is a pillar in my community and definitely going to be missed, and (he) touched so many lives," said Gina Maria, a 40-year-old teacher who lives in the community.

Gliniewicz's death is the third law enforcement fatality in Illinois this year, according to the Law Enforcement Officers Memorial Fund. It says firearms-related deaths in the U.S. are down 13 percent this year compared to the same period last year, Jan. 1. to Sept. 1; there were 30 last year and 26 this year.

The Associated Press contributed to this report.