Sunday marks one year since Bardstown police Officer Jason Ellis was ambushed and killed on his way home from work.

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Sunday marks one year since someone ambushed and killed Bardstown police Officer Jason Ellis on his way home from work.Case timeline | Mobile videoDespite hundreds of tips, the case remains unsolved, which is rare for an officer death.View images of memorials at the scene"It's been tremendously difficult, more so than most investigations we work," said Lt. Jeremy Thompson with the Kentucky State Police.Investigators say difficulties include lack of evidence.The time of the attack, between 2-2:30 a.m., when it was dark and traffic was scarce didn't help either."This isn't I-65. It's the Bluegrass Parkway," said Thompson. "The number of houses and people around here, there's no traffic cameras. There's no witnesses around. Just the rural nature in it of itself makes it a complicated investigation."Ellis had stopped his marked car to clear brush from an exit ramp off the Bluegrass Parkway.“We don't know that he was 100 percent the target. It could've been another police officer. It could've been just a random citizen and unfortunately we've not been able to determine that yet,” said Thompson.KSP's suspect profile is fuzzy, but Thompson said it is unlikely the crime was carried out by a lone gunman.“We believe that either a co-conspirator, a spouse, an estranged boyfriend/girlfriend, someone knows something," he said.Flags and crosses line the exit ramp off the Bluegrass Parkway."It's hard to comprehend the loss," Thompson said.There are also emotional difficulties when the victim is a fellow officer."You don't typically see someone in a uniform with a gun belt on with a ballistic vest," Thomas said.Most police deaths occur responding to situations and the killer is known immediately or identified a short time later.In this case, KSP thinks the key is someone's conscience kicking in."Be courageous and just come forward and give us that one little bit of information to help us solve this case," Thompson said.Ellis' slaying has drawn national attention and with it added pressure to catch his killer.Thompson said solving this isn't about investigators."It's about Amy and her family and, to a lesser extent, the Bardstown Police Department and then the community of Bardstown itself, but first and foremost, a widow and two orphaned kids they need to know who killed their husband and father," Thompson said.The reward money now stands at more than $200,000.To leave a tip, all 270-766-5078 or email elliscaseetips@kentucky.gov.