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ARAPAHOE COUNTY, Colo. — An arrest was made Tuesday in a nearly two-decade-old homicide.

In 1999, Arapahoe County prosecutor Rebecca Bartee was found dead inside her apartment. A recent tip led investigators to an apartment complex in Centennial where the victim’s body was found 18 years ago.

Deputies said it’s the same complex where the suspect Robert Williams lived in 1999 and now.

“This isn’t a case that’s been cold for five years or seven years — this is 18 years,” Arapahoe County Sheriff’s Office spokeswoman Julie Brooks said.

Bartee, 41, had only been working in Colorado for a few weeks at the time she was killed. She moved to Colorado from Hays, Kansas.

The prosecutor was last seen at work at the Arapahoe County District Attorney’s Office on a Friday. Bartee’s body was discovered on a Monday after she did not report to work.

The 70-year-old Williams was a neighbor of Bartee. After all these years, Williams was living in the complex where Bartee’s body was found.

“I never thought the fact that there might be someone living here that could be tied to murder as far as that long ago,” a surprised neighbor said.

After looking at Williams’ photo, neighbors said they didn’t recognize the now-senior citizen and can’t help but wonder what the motive might have been.

Deputies said a tip from someone to a local news reporter, forwarded to sheriff’s investigators, led deputies to dust off the old files and develop enough probable cause to arrest Williams.

Court records are sealed, so it’s not clear what led deputies to zero in on Williams. New crucial developments in a nearly two decade-old case are considered extremely rare.

“To make an arrest in a cold case, it is difficult because people’s memories fade, people move, people who might have information don’t realize they have information,” Brooks said.

Brooks said Bartee’s family members, who live out of state, we’re thankful and shocked when they learned an arrest was made.

Williams is scheduled to make his first court appearance in Arapahoe County on Thursday morning.