running into your teammates(s)

[cmtsguy22]

Situation: bases loaded. batter hits ball back to pitcher. pitcher throws home to force out R3. catcher throws high to 1B and batter-runner is safe at first. R2 decides to run home. R3 that was forced out already is still in the field of play between 3B and HP. R2 runs into R3, who again is already out, and they both fall to the ground. R2 gets up and slides under the tag and he is safe. The umpire didn't see the 2 guys collide. Question is, should R2 be out also for running into R3? Would R3 who was forced out be considered a coach now since he was forced out or is he still a runner since the play is still going on??