The flight instructor of the multi-engine, retractable landing gear airplane reported that, shortly after touchdown, with the pilot receiving instruction at the flight controls, the pilot was simulating max braking, the airplane began to veer left. He announced, “easy on brakes and back on center line.” The airplane continued to veer left, he started to apply right pressure and stated, “my controls off off off.” He heard a sound similar to a flat tire, the left main landing gear collapsed, and the airplane exited the left side of the runway. The pilot receiving instruction reported that when the airplane touched down, it immediately began to veer left. Despite multiple control inputs, the airplane continued to veer left. The flight instructor assumed the flight controls and continued to apply max right rudder. The left main landing gear began to chatter, then collapsed, and the airplane exited the left side of the runway. Postaccident examination of the airplane revealed that a large flat spot on the left main tire casing along with a large hole in the tire and tube. The left main landing gear actuator arm was found bent. It’s likely that during the landing roll, as a result of a side load imposed on the left main landing gear, the landing gear actuator arm was able to bend, which allowed for the landing gear to become unlocked and subsequently collapse. The airplane sustained substantial damage to the left aileron and left wing. The flight instructor and pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation, other than the flat tire.