Peter Brumis knew something was very wrong after he dropped into the chute near the top of Echo Peak and felt his knee crunch as the joint gave out.The 36-year-old South Tahoe resident admits he broke the very first rules of backcountry skiing when he headed out alone late in the day. The friends he'd called all said they were busy, but the snow was too good to resist. Brumis started his descent just before 3:15 p.m. on Jan. 2. Other than a few snowboarders who'd dropped in before him and his dog, Cody, Brumis was alone. There was no …