Hard slab avalanche triggered sympathetically from skier. Crown on slope rollover. Weak layer not certain. Most pits have been failing either on buried surface hoar below MLK crust or another buried surface hoar layer higher in the pack. This part of the slope has seen a lot of wind in the last month. Bed surface was very smooth. I did not venture out to investigate due to lots of hang fire. Initial slide sympathetically released a second slide on an adjacent ridge to the southwest and approximately 200 feet below the original crown face. One skier descended with no problems. Second skier triggered slide 8 turns down the slope. Flank was approximately 50-75' from second skiers tracks. Debris was packed deeply on uphill sides of trees. Did not see how far it ran but I am guessing it ran full track into the trees below.