Police have not released information on how he was killed.
"I can't get into details about that," said Lt. Dave Smith of Sterling Heights police. "I can tell you that we know it was a homicide."
Blackmon, who was arrested Monday, is charged with first degree murder, felony murder, armed robbery, illegal use of a credit card.
"They had a relationship so she had visited him on several different occasions," Smith said.
FOX 2: "And this time she decided to rob and kill him?"
"That's how it worked out, correct," Smith said.
Police are investigating if there were other suspects involved in the case.
Smith said the case should serve as a warning to people looking for relationships online.
"Be careful about any internet relationships that are set up," he said. "This relationship began off of Craig's List and it may not be the best location to be (finding) people to establish a relationship."
"Sadly, the dangers affiliated in conducting business with a complete stranger through Craig's List has resulted in another tragic loss of life," Macomb County Prosecutor Eric Smith said in a release. "I commend the men and women of SHPD for their unwavering commitment in solving this homicide.
"My office will take every step necessary to bring justice to the family of Michael Freeland."