GAITHERSBURG, Md. (WUSA) -- A man was convicted in the May stabbing death of a 12-year-old girl in Montgomery County, police said.

David Rich Hang, 42, was convicted in the murder of 12-year-old Jessica Nguyen, his stepdaughter.

Police say Hang was married to at least one other woman, maybe more, in a news conference Wednesday morning. He currently lives with his other wife. Hang may have been involved in some kind of immigration scheme, by marrying multiple women, police said.

Police stumbled upon DNA evidence on the sheath of a knife found next to Nguyen's lifeless body, in the basement of the home on the 700 block of Raven Avenue in Gaithersburg on May 31st, earlier this year.

There were footprints at the murder scene as well, that matched Hang's shoe size, according to police.

It took months to charge Hang, because there were so many people living in the house.

"We had to eliminate each person in the house as a suspect," police said in the news conference.

Hang had taken off of work that afternoon and entered the home, probably with a key, because there was no sign of forcible entry, police said.

"I can't understand how someone could be so cold and heartless, that he could kill an innocent child like this," Montgomery County Police Chief Thomas Manger.

Hang's sentencing is scheduled for October.

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