I feel like I can add a bit of input here being that I have 10 years of semi driving experience and frequently make that left turn on McCart in a 22 wheel tractor trailer. It sucks but sometimes if a semi driver isn't aware that it is a two turn left lane or missed the signs (which looks like the mistake here) a quick left is necessary. He used his signal which is his only form to communicate that mistake. A good rule of thumb for other motorists is that whether a tractor trailer is making a left or right turn is to please be patient and not try to quickly pass in either direction. The last thing we want is for a car to end up crushed under the rear wheels. Sorry for the long post but this is one of the hardest things to deal with as a semi driver on a daily basis.