BOULDER, Colo. -- The Boulder County Sheriff's Office is investigating a case where a couple tried to fight off an apparent home invasion suspect and eventually killed him.

The man's body was found on the front steps of a home, located on the 100 block of Poorman Road, off Sunshine Canyon, about three miles west of Boulder.

Deputies say the masked man rang the doorbell of the couple's home just before 10:30 p.m. Monday. When 59-year-old Becci Starr answered the door, the suspect tried to force his way into the home with a water pistol, she said.

Starr screamed and tried to fight him off with a baseball bat, she said. The intruder then dropped the toy gun and took out a knife from his pocket and tried to attack her again, she said.

Starr's husband, 56-year-old Scott Mattes, said he heard her screams and ran down the stairs to her side. Mattes tackled the masked man outside the front door and struggled with him for a few minutes. Mattes eventually wrested the knife from the intruder and stabbed him in self defense as Starr took the bat and struck the man again, the couple said.

Mattes tried to resuscitate the suspect after he was no longer deemed a threat, but he died at the scene, said Sheriff's Lt. Phil West.

"The main thing I heard was (Mattes) saying, 'Breathe! Breathe! Try to breathe.' And Scott was saying, 'Get somebody up here. Get some help here,'" said Mattes' neighbor Dale Hursch.

Mattes suffered minor injuries and was taken to Boulder Community Hospital where he was treated and released.

The suspect is said to be a white male in his 20s or early 30s. He has not been identified. His fingerprints were run through the Colorado database but no match was made. A nationwide search of fingerprints was underway.

An autopsy was scheduled for Wednesday.

Sheriff’s investigators were continuing their investigation Tuesday.

The couples' actions may fall under Colorado's "Make My Day" law. The state law, passed in 1985, allows homeowners to use deadly force to defend themselves, their family or their property "when another person has made an unlawful entry into the dwelling" and when they feel that the intruder "might use any physical force."

One of the things investigators must determine is if the masked man made entry into the home. They're also trying to determine if the man knew the couple or the couple knew him.