The time between taking Carrie's picture and firing the shot, killing the victim in the square, doesn't allow time for the sniper to get from the square to the building.
There is no such place as "Jamaica state".
When handing Saunders his gyro in the beginning of the episode, Carrie mispronounces the name: Gyro is pronounced "yee-roe," not "jie-roe."
It's surprising that someone who remembers literally everything she's been exposed to hadn't heard that before.
The medical examiner, Joanne Webster (Jane Curtin), says that a victim was shot from an angle of "120 degrees". If 0 degrees is horizontal, then 90 degrees would be vertical. There's no need for angles greater than 90 degrees. The shot was fired from "the fourth floor", and Detective Burns estimates the distance was 150 meters. Assuming 120 degrees means 30 degrees above horizontal, the distance would be double the height from which the shot was fired, which would be 75 meters (250 feet), well above the fourth floor.