A B737 First Officer discovered at departure time that radio active HAZMAT was not properly documented nor secured in a baggage pit and so the crew had the material removed before push back.

Narrative

Improperly loaded Hazmat bumped by crew. At push back; Gate Agent passed HAZMAT copies into cockpit; rushing to get signed. We realized the paperwork was not filled out properly; i.e.; information as to what pit cargo was in was left blank. Ramp Agent was found and was hesitant as to where the HAZMAT was located. I informed the Captain of my concerns that there was a lot of confusion over the HAZMAT and since it was push time; paperwork wasn't filled out properly; and HAZMAT was listed as radio active I wasn't comfortable taking it. Ramp Agent said they would see where it was located and let us know. I went to ramp to inspect Hazmat and found it located in pit 5; just tossed in there. HAZMAT was not properly stowed (i.e. secured to floor) as required for radioactive material. We bumped HAZMAT. Ramp crew didn't understand why. A ramp supervisor asked why we were bumping it and I told him 'late paperwork; improperly filled out paperwork; and not secured properly.' He told me that sounded good and that they were having problems with the ramp and HAZMAT.