General assumptions: It is best to murder Tyler Colvin as a first victim especially that he doesn't walk to locations where you should be more careful while staying hidden.
Tyler Colvin travels between two points on the map and the first place visited by him is a first floor of the convenience store (a building located left from the starting place). As mentioned earlier, unauthorized persons do not have an access to the first floor, so it would be best to distract a store employee by turning on a radio. Before getting to the first floor make sure that Tyler is not currently there.
After getting to the first floor, you have to decide how to get rid of Colvin. The least original way is to shoot him or strangle him after he gets into a room. In this case you should hide behind the door or inside the closet and wait for the right moment.
Another method of killing Tyler is using a gas stove and shooting it to make an explosion. Start with turning on the stove. After that, hide in the closet and wait until your target starts walking to the stairs leading to the ground floor. Quickly exit the closet and shoot the oven. If you did everything according to the plan, explosion will be big enough to execute your target.
Another way of getting rid of Tyler is using the remote explosives locate on the first floor. Arm explosives and carefully leave the building. Wait until Tyler enters the building and gets to the first floor. Only after that detonate explosives (screen above).
Another place visited by Tyler is a square located in front of the car garage. Also in this case I do not recommend attacking directly your target, but using a trick. The plan is to eliminate Colvin in a gas pump explosion. Start with locating a gas pump shown on the above screen. Make sure that no one look at you and interact with the pump to spill the gasoline.
Wait until Tyler gets here and stops in the gasoline puddle. If you play on lower difficulty levels, it is enough to place yourself behind one of nearby parked cars and shoot at the right moment (you might use a silencer).
If you play on higher difficulty levels, the safer solution is to shot from the upper balcony shown on the above screen. But unfortunately it is connected with getting to the first floor of the garage, so you have either to sneak silently or use the proper disguise (e.g. Hope policeman). It is worth noting here that gas pump explosion will start a series of other explosions, so you have to quickly walk away.
A complete different way of execution of your target is shooting Tyler with a sniper rifle. As for reminder, a sniper rifle Ilyon R700 can be found on the first floor of donuts shop and in order to get there you have to distract or remove a guard watching the stairs.
The best place to shoot a sniper rifle is a balcony of the car garage (screen above), especially that a successful action is connected with completing one of additional challenges. Aim one of the shutters of convenience store and wait until Tyler appears there (in the meantime watch out for other characters who can appear on the balcony). After killing your target, holster the weapon and leave the balcony.