CHICAGO – A Fox Lake, Ill., police officer shot and killed while chasing three suspects Tuesday morning was a 30-year veteran of the force who went by the nickname "G.I. Joe" and was married with four children.

"He's got four sons who are going to have to go on alone," said Terry Resetar, mother-in-law of the slain officer, Charles Joseph Gliniewicz, 52.

Gliniewicz radioed shortly before 8 a.m. while on routine patrol that he was going to check on some suspicious activity, Lake County sheriff's spokesman Chris Covelli said during a news conference.

He then radioed that he was in a "foot pursuit" but communication was lost after that, Covelli said. Other officers found him shot, he said.

Gliniewicz was discovered in a marshy area, stripped of his gun and other gear, said Lake County Undersheriff Raymond Rose. He died at the scene, the undersheriff said.

Police established a perimeter and sent helicopters into the air as they sought three suspects, described only as a black male and two white males, Rose said. Several canine units were also dispatched, as well as SWAT teams in camouflage.

Scores of officers searching

With the help of U.S. marshals, teams of police from throughout the county searched surrounding woods and businesses. By Tuesday night, no arrests had been made as more than 100 police officers continued the search.

Friends and colleagues remembered Gliniewicz as fun-loving and optimistic and dedicated to his work.

"This should never happen. Joey just loved his job," said Thomas Poulos, a retired Waukegan, Ill., police officer who said he went to high school with Gleniewicz in Antioch, Ill. They both graduated in 1981, Poulos said.

They stayed in touch and saw each other at local events and reunions, Poulos said, and it was clear that Gliniewicz enjoyed his job. Gliniewicz helped with the police department's explorers program, which allows young adults to look into careers in policing.

"Loved his job, loved his kids, loved his wife, and he loved those explorers," said Poulos, who now lives in California. "He was just a delight to be around. … Not a bad bone in his body."

Fox Lake Mayor Donny Schmidt called Gliniewicz "a very dear friend."

"We lost a family member," he said at a news conference.

Rose said police across Lake County knew Gliniewicz for his affiliation with the local police explorers program.

Impact on young people

"He, as the leader of that, had a tremendous impact on a lot of young people in the county," Rose said.

Illinois FOP President Chris Southwood released a statement: "Today the Fraternal Order of Police lost a fellow member and brother who died heroically serving his community. Our thoughts and prayers go out to the slain officer's family, friends and fellow police officers. He leaves a legacy of several decades of service to Fox Lake for which we are humbly grateful."

Residents in the area reacted with shock as armed police patrolled their neighborhoods and helicopters thumped overhead.

Jill Heyn and Brad Pekarik live near the shooting site. "My neighbor came out hysterical," said Brad Pekarik. "It's not a good thing. Everybody's a little crazy these days."

Jill Heyn said it "feels like our paradise has been spoiled. It's just one story after another. Blue lives matter."