Swanson threw TD passes of 61 and 42 yards to Tyler Kraus, 45 yards to Ryan Mullen and 51 yards to Mayr, and also scored on two 10-yard runs - all in the first half. He completed 7 of 14 passes for all 251 of his passing yards in the half.
"Our offensive line was manhandling them and our receivers were getting downfield and catching the ball," said Swanson, who threw for more than 1,900 yards in the regular season. "From the very first touchdown, the excitement rose on the field and you could see it in the guys."
Mayr rushed for 132 yards on 13 carries, including a 24-yard touchdown in the third quarter that made it 48-0.
"They were trying to get to the quarterback, and why wouldn't you?" South Carroll coach Gene Brown said of Walkersville's defense. "But it left some holes for the run, and Brad made some plays."
When pressured, Swanson scrambled for more big plays, including his TD runs. He finished with 79 yards on 12 carries.
"I told the guys, 'We're coming in here not satisfied,'" Brown said. "Because teams that come in satisfied get beat."
Antoine Crawford rushed for 58 yards on nine carries - most of it coming on one 37-yard scamper - to lead the Lions (7-4). Quarterback Dave Berry ran 5 yards for a touchdown on the first play of the fourth quarter and Ricky Divel fell on a blocked punt in the end zone later for Walkersville's other score.
South Carroll (10-1) will host North Hagerstown next weekend.
"It's going to be a big advantage playing here, especially (if we play) the way we played tonight," Swanson said. "We're ready to pick it up a notch and take it to North."
Brown said he's seen the Hubs play this season and left impressed.
"They're an excellent team," Brown said. "They're well-coached, they're excellent on defense, they're a scary team. I like the win, but I'm not going to enjoy it for too long because we have to prepare for North. ... It doesn't get any easier."