Kentucky cops investigating the ambush murder of a colleague have been receiving death threats including one message that warned ominously "there is more to come."
Among the threats was a letter that is being examined by the FBI's questionable document experts.
The Bardstown police department began receiving the threats following the death of Officer Jason Ellis, 33, who was gunned down when he got out of his car to remove tree debris from a highway off ramp while on his way home.
Bardstown Police Chief Rick McCubbin told ABC News the threats have come in the form of phone calls and social media messages. One message read, "one down, 20 to go," referring to the small department where officer Ellis had served for seven years.
"To my knowledge, no other law enforcement agency in Kentucky has received any type of threat," McCubbin said.
The chief indicated the threats are not credible.
"It's just hopefully someone who is half nuts and the other half is on drugs," he said.
Nevertheless, Bardstown police department now has two officers instead of the normal one responding to all calls.
"If he will shoot and kill one police officer, what would prevent him from doing it to another. We want him in cuffs yesterday," McCubbin said.
The police are also receiving tips about Ellis' killing, but have no suspects in the murder, the chief said.
Ellis was on his way home last month when he stopped about 3 a.m. on May 25 because of tree limbs in the road on exit 34, the same ramp he took every day off the Blue Grass Parkway in Nelson County. The exit is 10 miles from Bardstown. When Ellis began removing the debris, Kentucky State Police say he was ambushed in a "premeditated attack" and shot multiple times.
Investigators believe the limbs were intentionally placed to draw someone out of their vehicle.
Ellis, a father of two, was an extremely active officer making a number of drug arrests in Bardstown. Kentucky State police have looked at Ellis' past arrests trying to find any connection to the ambush.
McCubbin says the death of officer Ellis has rattled the entire town of 12,000 people, located 40 miles southeast of Louisville.
"I hope we arrest the person because if the community got a hold of them, that person would much rather be in jail," he said.