Police in the St. Louis area say an Illinois woman and her two young children who were found dead in their Illinois home were murdered, and a search is on for their killer.

Major Case Squad Deputy Commander Jeff Connor said 31-year-old Sherri Coleman and her sons, Garrett, 11, and Gavin, 9, were discovered Tuesday morning by Chris Coleman, their husband and father, Tuesday morning.

Investigators still don't have a cause of death and have made no arrests in the case. They were asking for the public's help, Connor said at a news conference.

A neighbor told St. Louis FOX affiliate KTVI that Chris Coleman was returning from his overnight shift at Joyce Meyers Ministries when he found his family dead at their Columbia, Illinois.

Joyce Meyer called Chris Coleman a "very dear friend" who has "experienced one of the greatest losses imaginable."

"(We) are grieving with him over this unexpected and devastating tragedy," Meyer said in a written statement released late Tuesday. "Words are not enough. He knows that our love and our sincerest prayers are with him."

Columbia is just southeast of St. Louis, across the Mississippi River. Columbia police have turned the case over to the Major Case Squad of Greater St. Louis.

Neighbors said the Colemans had been receiving threatening letters and that their mailbox had been tampered with in the last week or so.

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The Associated Press contributed to this report.