Air carrier First Officer reported being notified of fuel-like liquid leaking from # 1 engine during line to depart. The engine was secured and returned to the gate for maintenance.

Narrative

As we were taxing to Runway XXR we stopped short of the runway; number 3 for take off. We started to smell and comment to each other about a gas like smell. Just then Tower notified us that the aircraft behind us noticed a fluid leaking out of the #1 engine. With the fumes we ran the quick action items for fumes and that started to help with fumes. And then shut the #1 engine down. Shortly after that we were made aware that ARFF (Airport Rescue and Firefighting) had been dispatched. We worked our way through the QRH for a fuel leak. The Captain ran coms between Maintenance; Dispatch; and ZZZ Opps. ARFF determined that it was fuel leaking but had stopped leaking after we shut the #1 down. With the leak stopped and ARFF behind us we determined it was safe to taxi back to the gate. Once at the gate we deplaned the aircraft and handed the keys to ZZZ Maintenance Cause: Luckily we were stopped and had the parking brake set. Team work and task management helped get through the required tasks. Conformation between pilots that we were safe and making good discussions moving forward do not add more issues to the situation.