Nothing is known about Gael before the apocalypse, but it can be inferred that he was involved in gang activity.
Gael is one of three men Nicholas Clark encounters on the road to Tijuana. He and his two companions are looting cars and killing to occasional survivor (i.e. the Older Gentleman). He and his buddies chase Nick briefly before giving up.
They encounter Nick later, walking among a herd of Infected. Gael becomes spooked by Nick's glare and becomes distracted, which allows the Infected a chance to overpower and devour him.