Does the gesture he made look similar to the one in the photo below, but without the other hand raised and the mouth open?
If yes, then it is sort of an informal Namasthe practiced among the town folk and some city folk who migrated from the towns or villages. It is polite and indicates that the person doing it is humble. You will rarely find a man of respect doing this unless he is carrying something in his other hand. Also, while using one hand, they usually go all the way up till forehead with the index finger instead of stopping at the collar bone and the thumb sticks out.
The person in the middle with headgear and large moustache you said was doing the gesture is the doorman and his only job besides opening the door is to salute the guests. You can find such person at many places in India and about a decade ago, he used to make decent money on tips too. Given that these guys have to hold the door with one hand and also because they keep doing the Namasthe, they tend to use only one hand so they can switch.
Also, searching for Google images of "Indian Doorman" will show you lot of pictures, but none with this gesture though.