The Suspicious Death of Kathy Wangler

What killed Kathy Wangler is known. Kathy, a wife and mother of two, was found dead from carbon monoxide poisoning in her upstairs bedroom on September 4, 2006. 

What is not so clear is how this happened.

Some believe it was a tragic accident set off by a faulty water heater inside the home. Others believe it was something more sinister and calculated.

Sources: 
1) https://www.findagrave.com/memorial/15657786/kathleen_s-wangler
2) https://www.oxygen.com/dateline-secrets-uncovered/crime-news/mark-wangler-convicted-of-killing-wife-kathy-with-carbon
3) https://en.wikipedia.org/wiki/Lima,_Ohio
4)https://www.reddit.com/r/TrueCrimeDiscussion/comments/1bi8jxs/did_ohio_anesthesiologist_mark_wangler_gas_his/ 
5) https://www.cbsnews.com/news/ohio-killers-son-wife-continue-innocence-crusade/
6) https://casetext.com/case/state-v-wangler
7) https://www.cbsnews.com/news/did-ohio-anesthesiologist-gas-his-wife-to-death/