I believe the most likely explanation is the crew stepped outside for a smoke (possibly after the “attempted firing” at an earlier strike), then realise there's more targets inbound. One of them tries to reach the truck to fire at the attacker, but he is way too late (and very alone) in his effort.
See pictures https://twitter.com/CorporalFrisk/status/994804846426558470
Russia diplomacy is the best of the world. What I don't understand, is why Israelis attacked Syria the night after V-Day celebrations in Moscow where Netanyahu was present. It gives the impression that Russia let Israel do that and it's not good for Russia image.
https://twitter.com/DinoAfuera/status/995772748944363520
LOL!
“OSINT analysis on the Pantsir/SA 22 Grayhound attack:”