Updated

A St. Louis man was sentenced to life in prison plus 25 years Thursday for killing a Vietnamese immigrant as part of a so-called "knockout game" attack.

Elex Murphy, now 20, was convicted last month of second-degree murder and first-degree assault in the April 2011 killing of Hoang Nguyen, 72.

Nguyen was walking home with his wife from a trip to a store when he was attacked by a four teenagers. Three other people were reported to be with Murphy that day, but no one else was charged in the case.

In the "knockout game," people are picked at random and beaten. The attacks are sometimes captured on cellphone video, and some have been posted on social media sites.

The defense argued that no physical evidence linked Murphy to the crime, and that another man's DNA was found in blood on glasses that had been knocked off the victim's wife, Yen Nguyen, during the attack.

Prosecutors said Murphy broke away from the group, grabbed Nguyen's shirt, and punched him so hard he fell to the ground. Murphy then hit Hoang Nguyen in the eye, knocking the glasses off his face.

Yen Nguyen, 62, identified Murphy to police and in court. The St. Louis Post-Dispatch reported that she told the court Thursday, through a translator, about the impact the attack has had on her life, saying she is left to feel "very lonely."

"When we came here, we came here as a couple," Nguyen said.

Since the trial last month, Nguyen has gained her American citizenship. She wore an American flag pin on the lapel of her blazer.

"My family is destroyed," Nguyen said in court. "But I believe this country is a country of freedom. Even though I am very lonely I will try to live, I will try to work hard."