Updated at 6:01 p.m. April 20, 2011:
Police have arrested Elex Murphy of North St. Louis and are holding him without bond.
A police investigation revealed the attack was part of a game which involves unprovoked attacks on innocent bystanders.
An investigation to identify other suspects is ongoing.
St. Louis police say they have arrested an 18-year-old man in connection with the beating death of a 72-year-old Vietnamese immigrant and the assault of the 59-year-old wife.
Hoang Nguyen died Saturday. He was beaten to death by a group of four people - two young men and two young women - as he and his wife, Yen, walked home through an alley after going to a Vietnamese market. Surveillance cameras captured the attack on tape.
Police say they will present the case the prosecutors this afternoon. They continue looking for other suspects.