1991 Chevy Silverado Braking Pulls To The Right

I purchased a used truck in August from a auction. The trucked passed Va. State Inspections with flying colors. One day while driving it, I had to stop suddenly. My truck made a "noticebly sharp" pull to the right. A couple of weeks later, I had to make a quick stop again at a stop light. The truck pull noticebly sharply to the right again when I suddenly hit the brakes. If I had not been paying atention, I could have struck the car in my right lane.

My front end has been recently aligned and my front tires are in great shape. If my front brakes passed inspection, what could be causing this issue?