Complex sentence: Up to 1971, the cannon was fired inside the stadium, however, an unfortunate incident with a rival school's cannon got all cannons banned from the Pac-10 (then Pac-8) Stadiums.
Split into simpler sentences: Up to 1971, the cannon was fired inside the stadium. However, an unfortunate incident with a rival school's cannon got all cannons banned from the Pac-10 (then Pac-8) Stadiums.