I looked up a bit on Virginia law.
Second degree murder includes felony homicide. Felony homicide is when someone is committing a non-murder felony and kills a person unintentionally.
VA Homocide Laws | Murder & Manslaughter Charges
There are two traffic laws in Virginia that count as felonies which might apply to this incident. The first is reckless driving, which is normally a misdemeanor, but can be a felony if the driver doesn't have a valid license and causes a death. I don't know if the driver in this case had a valid license.
Virginia Code Title 46.2. Motor Vehicles § 46.2-868 | FindLaw
The second traffic felony that might apply is for leaving the scene of an accident in which injury or death occur, or property is damaged. That is a requirement unless injury forces the driver to leave, and even then, the driver is required to make their name and license number known as soon as reasonably possible. Failure to do so is a class 5 felony if injury or death occur.
Virginia Code Title 46.2. Motor Vehicles § 46.2-894 | FindLaw
Based on this, charging the driver with second degree murder seems likely to succeed in court, even if intent cannot be established. Assuming no intent, that the driver left the scene of an accident is pretty irrefutable, and as all the reports I have seen indicate that the police went and arrested the driver, rather than the driver making himself known to the police or victims, he almost certainly is guilty of the class 5 felony for leaving the scene of an accident. That, in turn, makes him guilty of felony homicide, which makes him guilty of second degree murder, based on my reading.
I am not a lawyer nor criminal law expert, and I am not saying the man does not deserve his day in court. I'm just pointing out that, even if there is enough evidence to cast reasonable doubt on the driver's intent to run into the crowd, he may still be found guilty of second degree murder.
Here's a link to the Title 18.2 code of Virginia as of 2016, which covers Crimes and Offenses Generally. Murder is dealt with in Chapter 4, Crimes Against the Person.
2016 Code of Virginia :: Title 18.2 - Crimes and Offenses Generally