The 25-year-old midfielder flew out of Buenos Aires on Friday bound for China to join Shanghai Shenua's growing pool of top international talent in a transfer reported to be worth $9 million.
An attacking midfielder, Moreno has spent almost two years at Racing, one of Argentina's "Big Five" teams.
His midfield skills excited Racing fans, but his performance fell off after he damaged knee ligaments early last year and was out of action for seven months.
Racing also struggled for form and are near the bottom of the standings in the Clausura championship which ends this weekend.
"You always want to be champion. One day you are, the next you're not. That's the way football is but I'll always be very grateful to the people at Racing," Moreno said early on Friday at the airport as he headed for China.
The gun incident last month exposed the aggression of Argentina's 'barrabravas', hardcore hooligan fans who wield power over clubs and players.
Moreno's transfer comes during a week when Argentine officials shut down a section of River Plate's stands after a fan stabbed another to death.
Officials also contemplated shutting down Boca Juniors' Bombonera in the wake of incidents last week when barrabravas lit illegal flares and an object thrown from the crowd struck a linesman in the mouth.
Many blame the violence in Argentine football on the high levels of impunity surrounding the barrabravas, who gain power through club and political connections.
Javier Cantero, the president of Racing's cross-town rivals Independiente, has vowed to eradicate the hooligans from his club. His fight was greeted with support from Independiente fans, but also a bomb threat at a school run by the club.
Cantero has asked for help from the government and the Argentine Football Association but complains he has received little more than lip service.
State-run television Futbol para Todos (Football for Everyone) is running a tagline during games reading "barrabravas 'no', fans 'yes'."
However, commentators say it will likely take much more to root out the hooligans, which means Argentina may find it increasingly difficult to keep local players at home and attract international talent like Moreno.