Lead Technician reported main cabin door slide disarm procedures were not followed by brake riding personnel; resulting in a door assist bottle being discharged and a partial slide deployment.

Narrative

At XA32 Company Operations called and requested line maintenance assistance on Aircraft X. I was told that; '...they are stuck on the plane; can't open the door and can't get out...'. I verified aircraft and location and called upon one AMT to assist. After some discussion and thought; I decided that I should evaluate and assist if necessary. As I approached the aircraft I could hear that the APU and packs were running and that the R1 door was open someone was partially looking out. The AMT I assigned to assist was already at the L1 door when I arrived. He was examining the door. As I ascended the mobile stairs I asked him to verify that the slide girt bar had not come dislodged. He said that he could see the girt bar. I immediately asked him to move so that I could better evaluate the situation. I saw that the girt bar was actually engaged in the spring sprawls/stops on the floor. I told the occupants to not touch anything and stay away from the door. I asked the AMT to move the airstairs to the other side to get the occupants out and I went to inform Operations that a Manager/Supervisor will be required because this may become an ISD (Inflight Service Difficulty). When I came back to the aircraft the AMT was ready to pull up to the right side of the aircraft and he informed me that he asked fleet service to bring another air stair. Both I and the AMT entered the aircraft through the R1 door. I took notice that the L1 door lever was in the up position and the arm/disarm lever was in the disarm position. I entered the flight deck to retrieve the safety pins for the door. Safety pin for the slide pack was on the slide. Safety pins were installed I handed my Leatherman to the AMT in case of an ISD (Inadvertent Slide Deployment) inside the aircraft. I proceeded to disengage the girt bar from the floor spring sprawls/stops. At this point I called another AMT to pull up AMM references to remove the slide. I asked the Fleet Service Agents what happened. One was training the other on how to brake ride the aircraft. I was given no information as to how the slide was engaged only that the Trainee was the one who attempted to open the L1 door. I called Name (ZZZ Maintenance Manager); ZZZ1 Supervisor/Manager; and Maintenance Control to apprise them of the situation. Once I got back to my desk; I submitted a request through maintenance online to remove Aircraft X from service; I printed out maintenance paperwork as well as Form Number for escape slide render safe checklist. I returned to the aircraft with two AMTs to remove the slide and free the door. Once the slide was removed we noticed that the door was still stuck and would not move. I suggested that maybe the door assist bottle may have been blown and we may need to leverage the door. The two AMTs worked that while I was answering phone calls from Maintenance Control; ZZZ Manager; and ZZZ1 Supervisor/Manager. The AMTs freed the door and it flung open. They also confirmed that the door open assist cylinder had been activated. All of this indicates that the L1 door was armed at the time one of the occupants attempted to open it. Proper and documented procedures were not followed by the occupants and it created a situation that could have caused damage to the airplane or themselves. Not to mention the inherent risk involved with the ensuing maintenance to safety and secure the slide.The Fleet Service personnel were inadequately trained and lacked experience in the necessary procedures to safely operate an Airbus door. Re-evaluation of the company's current policy that allows Fleet Service employees to actively conduct what has been traditionally known to be an Aircraft Maintenance or Flight Crew function.