Mr. Kaine (the VA Gov) may very well know the technical difference, and what he said is technically correct.
Every person killed at Cho's hands on April 16 was shot with one of two firearms, a Glock 19 9mm pistol or a Walther P22 .22 caliber pistol. Both weapons are semiautomatic, which meant that once loaded, they fire a round with each pull of the trigger, rather than being able to fire continuously by holding the trigger down.
this is a point-of-issue matter. Ask yourself, what is the point here? What is he trying to differentiate between? It's simple folks, he was simply making the simple point that SMGs/assault-rifles/machine-guns/etc. were not involved.
Yes, you are also correct in noting that he did not complete the statement with the set of technical details regarding what happens in between those pulls of the trigger, but that doesn't make the statement wrong. On a daily basis every one of you make the same type of statement somehow or another and don't even think about it.
Example:
When you pick up the television remote control and hit "Power" are you really turning the TV on? No... not really. "Turning the TV on" implies that you - yourself operated the switch that completes the circuit necessary for the television to function. Did you do that? No. Instead, you pushed a button on a infrared-emitting device which then sent a signal in the form of light to a sensor on the television, which then in turn triggered a relay which in turn completed the circuit necessary for the television to operate. In fact, for that matter, the television was already somewhat "on" in the sense that the sensor and relay, components of the television, were already receiving power prior to any action on your part.
Despite this however, we commonly would just say, "I turned the TV on." We do this because otherwise we would lose the attention span of whomever we're addressing (as I likely have).
However, apparently according to the logic applied by some in this thread, failure to specify EXACTLY what happened when you pushed "Power" on that remote-control, makes you unfit for operation or consumption of television, and you sure better not ever even think about getting involved with any regulatory body that has any involvement with television-sets and related equipment.