So my friend and I are running RotRL and we switched off GMing after the 1st module. My PC told the rest of the crew that he was going home to Magnimar.
The chase ended up running them out onto the Irespan for an ambush. However, the PCs managed to kill the runner in the first combat round, before his friend could climb up onto the bridge. His companion screamed out in anguish, prompting the PCs to look over the edge, and witness him drink a potion of feather fall and begin falling down to the Underbridge.
That's when our Paladin decided to jump after him...
After much debate, I let him score a hit on the enemy as he fell by. He still took a pile of falling damage, though not enough to kill a 7th level character. (Fun fact, max falling damage averages 70 damage.) The Half-Orc Oracle (who just took his first level in Paladin) followed him down about 2 rounds later.
Let your players relax and get back on the investigation after dealing with the fall-out. They don't need another ambush after the one they just had.
For one, Underbridge is a large area. Perception check should be required to notice the figures falling.
For two, I doubt X spends all her time waiting for people to jump off the bridge so she can swoop down and attack them. She's presumably busy with scouting out for proper victims.
And as far as a murder investigation goes - I'm assuming you're having the stalker continue to be in assumed form after death? Even if that is the case, its internal anatomy (which does not change) will easily prove to investigators that the body is something abnormal. Also, I doubt murder investigations happen in Underbridge often…
I don't think anyone in Underbridge is gonna mess with two big paladins who just plummeted from the sky and stood up. Though this does give them a great chance to pick up a bard as a cohort, since they both just grabbed Leadership. Looks like I need to write up a couple of bards.