There isn't a fire risk. The doors all have emergency releases (big green buttons marked emergency release) next to them which disable the magnet. Also, they will usually disable automatically allowing them to be opened in an emergency.
Also, failing all that they can be forced open by using not too hard a pull/push. I've seen it happen before. I saw an irate passenger who missed a flights pull open doors at one UK airport and try to walk down the jetty. Staff stopped him after about 2 footsteps, and I'm not sure exactly what he was trying to achieve anyway, but the fact remains these doors are not 100% secure, so there isn't any risk to life of being stuck behind them.
Not saying that what happened was good, but there was no risk of death involved.