What you are describing is effectively a guided missile and not a bullet per se. There are forms of artillery ammunition which could perform feats similar to what you describe. The Excalibur artillery round will attempt to hit a predetermined point programmed into its GPS system, using GPS signals to navigate and small fins to guide it onto the target. The Bofors STRIX 120mm mortar shell has an active infrared seeker which allows the shell to autonomously move to the target (the around was designed to be used against tanks). An earlier idea was the 81mm Merlin mortar shell, which had a millimetric wave radar to guide to towards a target.
So the idea that a ballistic round can mount a seeker head or GPS and direct itself towards a target is hardly far fetched. The real issue is the bullet from a firearm is far smaller than an artillery shell, so the room for the seeker mechanism, computer, actuators for the guidance system and a power source becomes extremely limited. This would make manufacturing such a system incredibly challenging, and each round would be quite expensive (a true "silver bullet", so to speak).
The other issue is the kinetic energy the round will deliver will be far less than a "dumb" bullet. This is mostly to do with the cross sectional density of the round. A standard NATO bullet like the SS-109 5.56X45 small arms round has a steel "penetrator" surrounded by a copper jacket which provides the aerodynamic shale and lubricates the round as it passes down the barrel. A "smart" round will have a lot of tiny machines and computer parts packed in the same volume, so weigh far less than the equivalent dumb round. Less mass means less momentum (the bullet will slow down much more quickly, somewhat like the way a ping pong ball will slow down much faster than a golf ball if thrown at the same speed). Even after taking that into account, when the bullet strikes, it will more likely shatter than penetrate, particularly if the target is wearing armour or protected by something solid (say a car door or the corner of a building).
So your bad guys will have ridiculously expensive rounds with absurdly short ranges, capable of causing injuries but not reliably killing the target.
If you really want to have expensive mayhem, have the killers mount a 7.62mm minigun on their car and hose down the entire area where the target is. It is much more reliable and probably far more satisfying for the shooter as well (the target is unavailable for comment).