Now, there's a trick!

It's possible that they'll be fine. Often cats look to us like they're
doing each other great damage when really, it's just play and
communication. A six week old kitten really can't be outside w/o
supervision - it's too young and dumb not to run right out in front of
a car.
Bring the kitten inside and keep him inside until he's at least a year
old, minimum.

Cats don't generally kill each other. The resident cat can see this is
a baby. He is asserting his apce, his age, his authority on the cocky
little newcomer and that is his right, awful as it may look to us.
Supervise when you can, pull big kitty off little kitty when it looks
like he's over-doing it, but otherwise they will work out how to share
the space if you give them both attention and love. It can be harrowing
for a while, but they'll probably end up the best of friends if you
just hang with it for a while.

And make sure the kitten gets neutered when he's big enough, and both
cats are flea'd and given feline leukemia shots.