we flight attendants usually dont open the door from inside. the gate agents will knock the door, so does the caterers, now if we gave them an ok sign upon arrival after disarming the door, they will crack the door open and we will push the door.
Caterers usually knock on the door upon arrival and the same thing applies. but if the plane was parked at the gate, they will knock and open it by themselves.
On airbus planes and from b747 and upward, the door will indicate that it is armed. but usually, its ok to open the door for a parked plane without passengers, the door on most planes (with the exception of the 717,727,737 and the DC9's,) will automatically disarm if opened from outside.
i think that door was cracked open from outside. since the handle is up