Several dead cops, a boat full of stolen money and no other alive witnesses minus an elderly couple whose testimonies would have been circumstantial. There is no evidence in their favour, who is gonna believe an entire police department went rogue.
shareAt first what you say makes you think, but drilling a little deeper:
1. You have to be proven guilty, not proven innocent.
2. The older couple was not circumstantial, they are eyewitnesses who were kidnapped by the bad people. I.e., the most powerful form of evidence.
3. There are decades of character witnesses (noble young church artist, idealistic truck driver vs despised sheriff and mercenary hooligans).
4. Lots of other evidence: the sheer amount of different guns and ammo used (all with fingerprints), the disassembled banister and jail cell, all the boats, the school damage, the church damage, security footage at the boat place, etc) could corroborate their story, and indicate it was 5 men chasing 1, and not vice versa.
5. Common sense which tells you that if a driver wanted to steal money he already has in his possession, he wouldn't have to go to these extremes (submerged truck, jetskis, and electrocution) to kill a bunch of strangers AND THEN RETURN ALL THE MONEY!