Apr. 21—In order to help Jefferson County Sheriff's investigators find the killer of a 20-year-old Arvada woman, rewards have been offered by Crime Stoppers and the company she worked for.

Eric Peterson said Alexa Bartell was working at Commercial Flooring Services in Denver as the Scheduling and Safety Coordinator.

The company is putting up $15,000 in reward money for information leading to the arrest of the suspect, or suspects, who threw a heavy rock into Bartell's moving Chevy Spark, killing her. That's in addition to the $2,000 reward from Crime Stoppers.

"We want to get the people who did this caught," Peterson said. "We need to get these idiots off the streets."

Peterson said he'd known Bartell since she was a child. Her mother, Kelly Bartell, is the Senior Accountant and the Secretary/Treasurer of the company, having worked there for over ten years. Alexa was the single mother's only child, he said.

Kelly Bartell went to the field where her daughter was found and laid flowers there Friday.

"She wanted to learn more and more. She was goofy and funny," Peterson said. "We were creating a position for her."

The best lead Jefferson County Sheriff's investigators had into the bizarre rock-killing death of Bartell disintegrated overnight.

The sheriff's office tweeted just after 10 p.m. Thursday night that a previously published truck of interest and its owner were not involved in Bartell's death.

Jefferson County Sheriff's investigators had tracked down that truck and its owner and released photos of the vehicle, but as of Thursday night that lead went cold. The hunt for suspects continued Friday.

Sheriff's officials said Alexa Bartell was talking to a friend on the phone in her yellow Chevy Spark when she suddenly went silent.

Bartell's friend tracked down her phone and drove to the location on Indiana Street and found Bartell dead inside her car, which was off the roadway in a field.

Jefferson County spokesperson Karlyn Tilley told The Denver Gazette once they identify a suspect, they will recommend murder charges.

Bartell's death is believed to be part of a larger overnight crime spree involving rock hurtling, Tilley said. She indicated that the rocks were the type that is used in landscaping.

The rock hurtling began at around 10 p.m. Wednesday night, ended just after midnight Thursday morning and included five vehicles. Other drivers whose vehicles were hit had minor injuries.

Bartell's was the fourth of the five known incidents.

Around 10:45 p.m. Wednesday, Bartell was driving northbound near the 10600 block of Indiana Street near Rocky Flats Wildlife Refuge when she was hit by the rock. According to JCSO, the rock was thrown possibly from a vehicle or the side of the road.

According to Facebook posts, Bartell, 20, went to Arvada West High School. Her friends are said to be devastated over her tragic death.

Jefferson County deputies provided the following timeline of events.

10:04 p.m. — Westminster — 100th Ave. & Simms St. — rock through a windshield. Driver not injured.

10:36 p.m. — Boulder County — McCaslin Boulevard and South Indiana Street (entrance to Rock Creek neighborhood) rock through a windshield. Minor injuries to the driver.

10:37 p.m. — Boulder County — McCaslin Boulevard and South Indiana Street (entrance to Rock Creek neighborhood) — rock hit a Toyota 4-Runner. Body damage to a vehicle, driver not injured.

10:45 p.m. — Jefferson County — 10600 block of Indiana Street — rock through a windshield of yellow Chevy Spark — homicide.

April 20 at 12:24 a.m. — Arvada — Highway 93 at Highway 72 — rock through a windshield — minor injuries to the driver.

The sheriff's office said they're working with Boulder County Sheriff's Office, Arvada Police and Westminster Police to gather information. They believe there may be additional victims.

Investigators are asking for any other possible victims to call the JCSO tip line at 303-271-5612.

They are also looking for anyone who might have home security or dash cameras that may have caught the vehicle driving by.

This story will be updated as new information becomes available.