Police identified the shooter as Joshua Glover, 21, of Peck. Deputy Police Chief Robert Lee said Glover shot and killed Danielle Weixelbaum, 18, and seriously wounded Montrell Pickens, 22.
A resident of a neighboring apartment, William Summers, 41, was killed by bullets that penetrated his wall, police said.
Two police officers were also shot when they arrived at the scene. Their wounds were not considered life threatening, police said.
The bodies of Glover and Weixelbaum were found when police burst into a second-floor apartment, said. Police believe the gunman killed himself.
Pickens was shot several times and was in critical condition, police said.
One of the injured officers was in surgery with a wound to the lower torso and the second was shot in the leg.
A motive was under investigation, Bassham said.
Police said Weixelbaum was the daughter of Glover's 35-year-old ex-girlfriend, reported CBS Witchita affiliate Eyewitness News 12. Police said the ex-girlfriend was Glover's intended target, but she wasn't home at the time, Eyewitness News 12 reported.
Interests listed on Glover's MySpace page, according to Eyewitness News 12, include body building, girls and guns.