Prior to Sean's first appearance in the first season Sean had moved to live in Wasaga Beach with his parents and went to school with Tyler, it was never mentioned how long their conflict had been going on for.
In the episode Under Pressure, it was revealed that one day Tyler stole Sean's Lunch money and they had a serious physical fight and Sean punched Tyler in the left ear. The result was that the blow of Sean's punch had been so hard that Tyler had been permanently deafened in the left ear. Then for Sean to avoid charges placed on him by Tyler's parents, Sean's parents forced him to move back to Degrassi to live with his brother.
In Back In Black, Sean, came back to Wasaga Beach for a visit he had brought his current at the time girlfriend Ellie Nash and his best friends Jay Hogart, and Emma Nelson. They went to the local beach and Sean was shocked to see Tyler working on the beach at the Jet Ski stand. Tyler was now shown to be wearing a hearing aid on his left ear. Sean told his friends who he was when Jay asked him who he kept staring at. Then Tyler noticed him too, he sure wasn't very happy to see him. Then at the stand Jay teased Tyler about being partly deaf, but Tyler went for Sean not Jay and they almost begun another fight. Then Sean's friends kept them apart. Tyler treating Sean like he was nothing but a lose cannon, snapped at him about how he was now being treated like a hero and how he had to get away this time because someone had died. Tyler had obviously heard the news about The Degrassi School Shooting and how Sean was the one who had stopped the perpetrator Rick Murray. Thinking Sean did this just to be a hero, not aware that Sean did this to save Emma and the rest of the school.Tyler then gave Sean a free Jet Ski Rental because he still wanted to make up for stealing his lunch money years before and possibly because he was a still a little afraid of him. Then when Sean was driving the Jet Ski at an alarming speed and on really powerful waves he nearly drowned. Then Tyler came in and saved Sean from drowning and they two possibly made amends after this.