Go to the Package level in campaign and select rally point Bravo. Set the difficulty to anything but easy.

Now start your game. Get to Doctor Halsey's lab and grab a jet pack.

Jet pack to the roof above the front door and wait for a banshee.

Note: you can also do this for the "If They Came to Hear Me Beg" Achievement.

Just turn on the turret closest to the lab.