Dao Tran is a member of the Born to Kill Vietnamese gang in the New York City chapter, a gang in rivalry with the Ghost Shadows, which has Chinese members. Tran, in a forbidden romance, was dating Helen Chen, the sister of rival gang member Johnny Chen, who abused her and made her participate in their operations.
When Helen was raped and brutalized to the point she was reduced to a hospital bed and braces, Johnny alleged to be out of the gang and accused Tran. When Tran was arrested, he accused Johnny of letting one of his accomplices rape her, as he scarred her in an initiation and made Helen participate in crimes, including being a lookout at the robbery where she was raped, which is why Tran tried to protect her.
After Johnny was arrested, neither gang or any gang was revealed to be responsible for Helen being brutally raped. A racist named Darrell Guan, born from the rape of his mother Susan by black-American serial rapist and murderer Harold Starnes, which led to Darrell being rejected by Chinatown and hating the community and his own race. (SVU: "Inheritance")