Manhunt continues for person who shot and killed veteran Illinois police officer
An armed police officer walks throughs a field as authorities take part in a manhunt in Fox Lake, Illinois, United States, on Sept. 1, 2015. Photo by Jim Young for Reuters.

More than 100 police officers using aircraft and canine units were searching northern Illinois on Tuesday afternoon for three suspects believed to be involved in the fatal shooting of a 30-year veteran police officer, officials said.

Fox Lake Police Lieutenant Charles Joseph Gliniewicz was found wounded on Tuesday morning after reporting that he was pursuing three suspects on foot, the Lake County Sheriff's Office said. He died later.

Officials have only described the three suspects as two white males and one black male. None were in custody as of Tuesday evening, Lake County Sheriff's Office spokesman Christopher Covelli said.

The shooting came days after a county deputy sheriff in Texas was killed in a hail of gunfire while refueling a patrol car at a gas station. A suspect in the Friday shooting was captured and has been charged with capital murder.

"Today, not only did Fox Lake lose a family member, I lost a very dear friend," Fox Lake Mayor Donny Schmit told a news conference.

Gliniewicz, a father of four boys and a decorated officer, was known around the village as "G.I. Joe" and dedicated to Fox Lake and his fellow officers, Schmit said.

Police with dogs and helicopters continued to search woods and swampy areas after three suspects fled the scene where Gliniewicz was shot.

On Tuesday evening, a group of officers formed a line and disappeared into dense trees and brush in a search for the suspects as bystanders watched across a busy road.

"I've lived here for 30 years and never had to lock my door until now," said Dan Christensen, 64, as a police helicopter circled above a nearby wooded area.

The suspects were on foot when the officer initially made contact with them, and they stole his firearm and other gear before fleeing, media reports said.

Covelli said local residents should remain indoors and report suspicious activity.

Officials ordered commuter trains halted, roads blocked and area schools locked down as they conducted a widespread search in a wooded area about 40 miles (65 km) north of Chicago near the Wisconsin border.

Federal marshals, Illinois State Police and units from McHenry and Lake County Sheriff's offices, many with drawn rifles, searched door-to-door.

The Federal Aviation Administration established a no-fly zone over the search area.

(Reporting by Brendan O'Brien; Additional reporting by Suzannah Gonzales in Chicago; Writing by Fiona Ortiz and David Bailey; Editing by Susan Heavey and Eric Walsh)