Why Rush In?

So there was body camera footage of an OIS (Officer Involved Shooting) that occurred November 3, 2015, where a 6 year old child was killed. This occurred in Marksville La, where a vehicle pursuit ended and a Deputy is seen in the video exiting his patrol car and running up towards the driver's side of the suspect vehicle. The deputy then opens fire on the vehicle. It appears that the driver had at least his left hand out the driver's side window before shots are fired. It is not known why the Deputy opened fire. In the passenger side of the suspect vehicle is the driver's 6 year old son. The investigation reports that the child suffered 5 gun shots and was killed. The driver was also shot and survived. The two officers involved in the shooting were arrested and are pending trial on 2nd degree murder and attempted 2nd degree murder. A link to the body camera footage is posted below.

From my training and experience, officers are trained not to immediately approach a vehicle upon stopping vehicle that was involved in a pursuit. You just don't know what's going on! Is the vehicle going to start moving again, different direction, will the subject bail and run, are they armed, is there a hostage or innocent person inside? Time is always on the police side, why rush in? This is a horrific and senseless loss of life, 6 years old, never to see 7....