Pottawattamie County Sheriff Jeff Danker said the man shot 48-year-old Patricia Harker around 2:30 a.m. and then turned the gun on himself before driving away.
The suspect also fired at another man in the house, but missed before shooting himself. Danker believes the suspect has a serious gunshot wound.
Danker said Harker and the suspect had been involved in a relationship, but had broken up a few weeks ago. Harker was taken to a Council Bluffs hospital in critical condition.
Deputies are looking for a silver Mercury Mountaineer which the suspect may be driving.