Critical clue led police to suspect Chicago doctor in deaths of Ohio dentist, wife

McKee was arrested in the Chicago area after detectives tracked his vehicle through neighborhood surveillance near the couple's home, according to court documents.

McKee's car "arrived just prior to the homicides and left shortly after," detectives said in the court documents. Investigators were able to identify the vehicle and subsequently link it to McKee.

McKee's neighbor, Gera-Lind Kolarik, told WLS-TV after his arrest that "he did not seem like somebody who would do something like this."

"I sat down with this man and talked with him at the pool, barbecuing, about what a beautiful day it is - and then he turns out to be [charged as] a killer," she said. "It's kind of shocking."