Breathing difficulty

We lost one of our pigs today approx 3months old. Around 3:00p, all was fine. My dad gave them some raspberries and they were fine when he left a few mins. later. Went back to check on them 5:00ish and one was having a very difficult time breathing - gasping for air - making a squeaking noise. Looked to me like a person having an asthma attack. I checked down his throat as best I could; nothing appeared stuck. Within minutes, the pig laid down and began to seize - convulse. Shortly thereafter, we lost him. Does anyone have any idea what could have caused this death so suddenly. It's not heat stroke - temp was about 75 degrees no humidity. They had plenty of water and a full wallow. Could pigs have an allergic reaction to raspberries? Any ideas?
Thank you