Gerard is a former member of SAS special forces and is currently working in PMC (Private Military Contract) from USA. His mentor, David is currently a wanted person as he betrayed the organisation and assist the Terrorist by giving away an important confidential documents of SAS to Terrorist. Gerard left SAS as he was falsely accused of betrayal with David.
Therefore, Gerard is perfect for a fast level up and striking solo due to his high attack power and reserve ammo. However, consider every damage taken due to his low HP value and low Kevlar strength.
Trivia
The selection icon shows Gerard wielding a Glock in Abyss3.
Certain CSO regions have different benefits for the player that uses Gerard. For instance, Gerard will reward players with 15% (20% if in internet café) additional points and EXP in the Taiwan/Hong Kong region if selected.
Gerard seems to have a long-distance relationship with Jennifer according to Zombie Shelter official trailer.