Jean was killed at the same time as the X-Men were fighting the Sentinels. I honestly haven't read the issue in a while, but are you saying that they were attacked by two different kinds of Sentinel at the same time?
I'm talking about the ones that killed the Reavers, chased whatsisface through the portal, and attacked the Hellfire Club. Colossus at the end of that comic is holding Jean's body in his arms, and they're all "OMG she's dead" even if they should be used to it by now.
X-Men... Uncanny X-Men 281.