Complex sentence: To make matters worse, while the pair have been in jail, Warren has killed Tara Maclay in an attempt to kill Buffy, causing Willow to go on a homicidal rampage; with Warren dead, Jonathan and Andrew are her next targets.
Split into simpler sentences: To make matters worse, while the pair have been in jail, Warren has killed Tara Maclay in an attempt to kill Buffy, causing Willow to go on a homicidal rampage. With Warren dead, Jonathan and Andrew are her next targets.