First, go to firefight then alpha site.

Next, when a hunter comes grab a spike rifle and get it over to those window things near where you respawn.

Now the hard part. Hit the hunter and kill it by melleeing it while it is about to fire.

If it slides on the window thing then you've done it right.

It should still be ready to fire, but it will be dead.

After a while the hunter will disappear but the glow from the weapon will still be there.