GREENWOOD VILLAGE, Colo. - SWAT officers found a man called a person of interest in the morning slaying of a former female co-worker dead from an apparent self-inflicted gunshot wound in a Greenwood Village apartment on Thursday evening.

After a three-hour effort to get the man to surrender, there was a loud boom about 5:30 p.m. as SWAT officers breached a third-floor unit at Carriage Place Apartments, at 4900 S. Ulster St. They found 51-year-old Robert Walter Lewis dead from a single gunshot to the head, police said.

Police said Lewis was recently fired for harassing Emily Weikert  at the national headquarters of CoBank, located at 5500 S. Quebec St. in Greenwood Village. Police did not immediately identify the slaying victim.

During the afternoon, officers using a bullhorn called the man's name, saying: "You need to give yourself up. Come out the front door."  Police radio traffic said officers believed the man had several guns.

The man was found dead just a block away from the Promenade Place Apartments at 5200 S. Ulster, where Weikert was found shot to death on a ramp between the third and fourth levels of the parking garage about 7:20 a.m., police said.

Police received a short 911 call at 7:21 a.m., but the caller couldn't tell the dispatcher any information, said Greenwood Village Police Cmdr. Joe Harvey.  Dispatchers told officers they they heard a woman screaming in the background, then the phone hung up.

"There were ... sounds of a struggle or something going on, so the dispatcher was working diligently to try and find out the exact location," Harvey said.

Investigators quickly used their resources to ping the cell phone and locate the apartment complex where the call came from.

An officer told dispatchers that the victim apparently was throwing things out of her car on the third floor of the parking structure, according police radio traffic recordings provided at RadioReference.com.

Later, inside the apartment garage, Harvey said, "We found signs of a struggle between the third and fourth floors of the parking structure. Folders and things like that were scattered around the floor."

"It looks like there were at least two gunshots," Harvey said, describing the killing.

"Her vehicle was in the parking structure, but she was found a little bit away from where her vehicle was located," Harvey said.

Investigators were looking for a green Jeep Cherokee in connection with the shooting. Officers confirmed to 7NEWS that they found the Jeep a couple hours after the shooting, parked near the Belleview Light Rail Station.

Police said the Jeep owner, who was not the man involved in the apartment standoff, was cooperating in the investigation.