That seems very likely. They probably had anti-aircraft and anti-missile missile systems fully armed and something either automatically mis-categorized the aircraft as a bomber or missile and shot at it or someone got nervous and trigger happy.
One likes to think that automatic missiles should be fairly accurate and confident in their assessments.
My question i've wondered : was the sensitivity deliberately set very high so as to provide counter-attacks no matter what? If that's the case, isn't it more than accidental?
Regardless of that, keep in mind that this happened hours after Iran bombed military bases of the country that runs the worlds largest airforce, and days after said military bombed their general.
Under these circumstances, it is entirely reasonable, normal, and expected that Iran would set their sensitivities to very high. It is also expected that doing so greatly increases the risk of an accident, which is why countries only do it when they have extra reason to suspect an attack is likely. The downside of a false negative is not 0. It is that who-knows-what gets bombed, and who-knows-how-many people die, causing who-knows-how-much damage to the country and its ability to defend itself in the future.
This situation is also how wars start. We got lucky that the mistake seems to be such that the big players (eg. the US) are willing to let this go as an accident and let hostilities return to their normal simmer.
There likely wasn't "human-scale" time to confirm identity. And specifically against a US adversary with stealth technology, it would make sense to have automated air defense systems on a hair trigger and human air defense systems with extremely liberal RoE.
What seems like it should have happened is that the international airport grounded all outbound traffic and parked all non-emergency inbound traffic in holding, until such time as Iranian air defenses could relax their posture to guarantee safety.
For anyone unfamiliar with the term, "RoE" stands for "Rules of Engagement".
The warning system is automatic, but it is a human (in this case on heightened alert) that pulled the trigger.
Of course you run.
And don’t forget there is a long history of using civilian craft to sneak military things in and out of warzones. Even using hospital ships to transfer munitions.
Western airport radar has gotten pretty good at picking up a plane within 2 miles from the runway but that's if it's specifically designed for it and positioned at the airport.
So some mobile missile launcher array would see the plane pop up a lot later. Someone sitting at the screen with their finger on the trigger could be startled by the first flight of the day and launch.