Episode 1 J was killed by a railgun from the year 3071.
Episode 7 J was hit by a Blue bird 2000 school bus which were built in the year 2000.
using linear extrapolation, when J gets injured, it'll be by a deadly item from the year 1847.
Now for those who don't know, the gun Tessa uses is a black gunpowder navy revolver which was invented in 1847 by Samuel Colt.
So my theory is simple, following the pattern, J will be shot in episode 8 by Tessa's revolver. Also if we continue with the linear extrapolation, we can conclude if we ever get an episode 20, J will be crucified.