When Reese and Walker surprise the mob guys at the stairway and shoot them, Reese says "We made it.' Walker says "We blew it." What is Walker referring to? They got the money. Was Walker angry that they shot the mob guys?
shareThis was a pretty significant deviation from the literary source material, but I understood it to mean that they'd killed unnecessarily in order to complete the job.
Reese says, "We just have to knock 'em on the head, Walker -- that's all!"
Then he comes out, guns blazing. It's pretty clear that Reese is a character with issues -- murdering the guards was rather over the top.
In the novel, I believe Walker (Parker) ambushes and guns down a dozen guys to get the money. They don't stand a chance.