Hello, and this is my first guide! I am new so please me patient. Anyway, here goes. Link to game: http://armorgames.com/play/1916/urban-sniper
Note that this guide is not "Perfect". It is the quickest way to beat the game. Not the highest scoring.
Level 1: Fairly simple. Shoot the guy in the hat, which he spawns in random corners. I would advise staying out of scope until you see an oddly shaped figure. When you do, shoot em' in the head. Now, shoot everyone in the cars. Everyone. Once there all dead, exit your mission.
Level 2: This one is a bit tricky. This time, you have 5 Targets. They all have sun glasses on, and are on the ( Random I Believe ) floor on the Ritz building. Shoot the one on the far right, and shoot everyone that comes on your cursor.
(This is now assuming you failed. I do not know how to complete the dog mission, though that level will be covered soon.
Level 3: Fairly straight forward. Kill the guy on the boat, then on the dock. The guy on the dock will run though, so put your cursor farther ahead of him so you can shoot him easily.
Level 4: Once again, a bit tricky. There is 1 target. Shoot him and you WILL miss. Shoot the chandelier above him and in the split second he stands up, shoot him. If you miss he will run again, giving you a little more time for the kill.
Level 5: This is the final mission. You have 5 targets, not including the pilot. First kill the pilot, so they cannot get away. Let ALL of them get on to the plane, then shoot them one by one when they get in their seats. You will have one more message, bridging this game to the sequel. Congrats, you beat the game.