Odd situation with BB who checked a raise

[JGlo]

I played in a small home tourney the other night when this situation occured.

Blinds 50/100 ; 10 handed

Blinds posted
UTG raised to 300, MP and CO both call, SB folds
BB (who had not been paying attention) looked at his cards and then said "Check"
We informed him that there had been a raise and he had to put in 200 more to play, he thought a second and then said "Raise" and raised it to $1000.

What is the ruling here? Is he allowed to do this? We discussed it a few minutes and decided that he could only call the bet due to his initial action. Your thoughts?