It's sad, but there usually has to be one cause of death. One of my patients was 'bashed' to death and resuscitated. The person was living in a vegetative state on a ventilator for many many months. Sadly, since pneumonia was the cause of death, the defendants could not be tried for murder
In this case, DT could be tried for felony murder of his brother. Even if he didn't allegedly run him over, he could still be tried. It doesn't really matter what exactly killed TT under felony murder.
Assuming state wanted to try him for that.