Wei Shen was born in Hong Kong but moved to San Francisco with his mother at age ten. Shen would become a police officer in San Francisco, before returning to Hong Kong to work as an undercover officer with the Hong Kong Police Department who is tasked with infiltrating the Sun On Yee Triad.
Shen successfully infiltrates the gang, and eventually becomes friendly with some members of the Sun On Yee, and quickly rises through their ranks, becoming a leader, or "Red Pole" of the Sun On Yee after the death of previous "Red Pole" Winston Chu. This leaves Wei caught between two worlds, that of law enforcement and the Triads.
It is revealed early in the story that Wei has a personal stake in the mission, as his sister may have been killed by the Sun On Yee, and later, Shen has several of his friends in the Sun On Yee murdered by a rival Triad, the 18K. Shen ends up personally involved with the conflict between the two rival Triads, and the internal power struggle within the Sun On Yee after the death of boss David Wa-Lin "Uncle" Po. Shen is attacked by the 18K at Po's funeral, at which point it is revealed that this was set up by corrupt HKPD superintendent Thomas Pendrew.
Battle vs. Mr. Chang (by SPARTAN 119)
Bai Ji-Shin Chang and two Triad enforcers got off a boat, the other two Triad staying on, one of the manning and MG42 on the top deck. Chang walked over to three men on the dock, gathered around a box of illegal arms.
"You have the merchandise", Chang asked.
"All right here", the undercover officer said, as he opened the crate, revealing a number of assault rifles. Suddenly, Wei Shen and two other undercover officers drew their sidearms and yelled "Police, hands in the air!"
Chang drew his AMT Hardballers as the enforces on either side of him raised their Uzis. Chang fired three shots, taking down a man to Shen's right , as he and his enforcers retreated behind crates and shipping containers for cover. Shen drew his USP and fired three shots at Triad with an Uzi, killing him.
Shen tried to get out of their, but the fire was too intense. A that moment, Shen got his break. One of the officers standing on the roof of a warehouse fired a short burst from his G36, killing another Triad and drawing the machine gun's fire. Unfortunately, the officer was killed by the MG.
Shen used the break to grab a G36 with an attached grenade launcher from the crate and fire a 40mm high explosive round at the boat where the gunner stood in wait. The grenade impacted right next to the MG42 gunner, blowing his shrapnel-riddled body off the boat. The explosion ignited the boat's gas tank, sending it up in a fireball.
Shen retaliated, firing his G36 at the SMG gunner, killing him with a headshot. Chang responded with a hail of .45 rounds, which forced Shen to roll over to the next cover, a shipping container. In the process, however, Shen dropped his rifle.
Chang advanced on Shen, pistols in hand, only to be surprised by Shen breaking from cover, USP in hand, firing off the rest of his magazine into him. Chang fell to his knees, then face down on the dock, his chest pierced by several rounds.
WINNER: Wei Shen
While Chang was highly skilled at dual wielding, and was himself a former police officer, it was decided that Shen, who was trained by two police departments, and had taken martial arts courses was better trained overall, both in firearms and melee combat.