Help! My heroes need to fail!

Okay, so I'm going to try to give as much background as I can. The Heroes have discovered that a series of seemingly random could-be-street-crime deaths are, in fact, an attempt to kill every member of a research team. They have located the still living members and split up to try to save them both. One (A) arrives too late. The other (O) arrives while the target is still alive.

Two things need to ultimately happen: O needs to fail to save the target, and O needs to follow the killer back to their vehicle, which will have some Vital Information for moving to the next location.

So... I need a way for O to fail, but not because he's stupid. He's supposed to be quite good at this heroing business and decent at strategy. But taking the right moves and reasonable precautions should still ultimately not be enough.

First thought: When you know someone is going to be killed, you move them to a more secure location. So he'd reasonably take that step. The most secure location is going to be intergalactic embassy. Perhaps the embassy has pretty good measures for ensuring that only people who are supposed to work there get inside? DNA scanners? Some reason to believe that the assassin Isn't going to be among the staff, at least easily. Things not accounted for: assassin getting on the guest list through political means, assassin hacking the embassy computers.

One of those things happens. More guards are sent to guard the target, the assassin replaces a guard and kills the target, chase to vehicles ensues.

Too easy?

Second Though: Bypass the whole "planning" aspect and have the attack hit as they're leaving the first location, in the "get you to a safe place" part of the plan. So it's not that the hero planned poorly, it's that he didn't really have time. Target panics, runs the wrong way, dead, pursue attacker. It shortcuts around having to come up with all the contingencies and having them fail. Maybe doesn't make the hero seem like an idiot. But it does rely on pretty damn close timing for two people traveling between planets to end up in the same place at the same time, such that 5 minutes either direction would have meant a complete getaway or complete victory. That may stretch credibility.

I was also thinking maybe he arrives early enough to set up a decoy. But then, the target still has to die, so somehow the decoy plan would involve not just sending them straight off world, which would be the reasonable thing to do.

Other ideas?