Maybe it was to emphasize the seriousness of the deadline. By capitalizing the word "DEAD", he was suggesting that if he missed the deadline, he would be in big trouble, so he exaggerates by saying he would die (or would wish he was dead).

Yes, agreeing with Richard also! "Deadline" doesn't hint that anyone would die. But "DEADline" highlights the other meaning of "dead" (=death, not end), so perhaps someone may "die" if the "dead-line" is not met?

yeh i agree with RICHARD.

maybe you can asked your friends directly