Hang was ordered held without bond during a hearing Wednesday in which he tearfully proclaimed his innocence in the killing of his 12-year-old stepdaughter, Jessica Nguyen. Her bloody body was found stabbed more than 40 times on May 31 in a basement bedroom of her family's Gaithersburg townhome.
His arrest has brought to light details of the unusual marriage. The wife's family had paid Hang to marry her, but he moved out very soon after the couple wed and had demanded a fast divorce so that he could have relationships with additional women -- something the family had resisted, authorities say. He was married to at least one other woman when he was arrested.
Hang had lived in the home where the crime occurred for parts of 2005 and 2006 while married to Nguyen's mother, but had long been estranged from her, authorities said.
Detectives initially found the case mysterious because there were no signs of forced entry in the home.
"There were a lot of people who were in the home or who had access to the home," said Montgomery County Police Chief J. Thomas Manger. "All of these people were the first people we looked at."
They soon zeroed in on Hang, 42, ultimately matching his DNA to the sheath of a knife or sword that was found without a matching weapon near the girl's body, court papers say.
He also called out sick the afternoon of the killing from his job at Montgomery County Ride-On, a local transit system, and was observed a day later with a swollen hand, court papers say.
Boot impressions found at the scene were the same size as his shoe, and cell phone records place him in the neighborhood during the time police believe the killing took place, authorities say.
Hang, who prosecutors say has used different names and moved from state to state, continued to have access to the townhouse despite being estranged from Nguyen's mother, Khen Kim Vu. The couple had wed in a "sham" arrangement intended to help Nguyen's mother earn citizenship, said prosecutor Stephen Chaikin.
Hang, who appeared via video hookup for a bond hearing, sobbed as he denied any wrongdoing. "I didn't do that," he said after Chaikin recited the allegations of the case.
He later said he had changed his name simply to make it easier for Americans to pronounce, and had moved around not for illicit purposes but because he was searching for a decent-paying job.
"I'm a good husband," he said, later adding, "I work hard and I always show up for work each day."
Nguyen's family was ushered out of the courtroom by Chaikin without commenting.
"What troubles me is that you have somebody as cold and heartless as that, who could kill an innocent child," Manger said at a news conference announcing the arrest.