LARIMER COUNTY, Colo. (CBS4) – Authorities are asking for the public’s help in locating a teenager who went missing Thursday night in Larimer County.

The sheriff’s office received a report at 8 p.m. Thursday that 18-year-old Ashley Marie Doolittle, from Berthoud, was overdue and had not returned home. Family members searched the local area and found her car, unoccupied, in the area of Lon Hagler Reservoir.

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(credit: CBS)

(credit: CBS)

Investigators responded to the area, and through interviews with family members, learned that Ashley had recently ended a one-year relationship with 18-year-old Tanner George Flores. He has been missing since 3:30 p.m. Thursday. It was also reported that Tanner was upset and distraught over the breakup.

“It’s reported to investigators that Tanner was very upset by the breakup and pretty distraught over the breakup after the one year relationship,” said Larimer County Sheriff’s Office spokesman David Moore.

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Search crews at Lon Hagler Wildlife Area (credit: CBS)

Search crews at Lon Hagler Wildlife Area (credit: CBS)

He drives a white 1999 Dodge 2500 diesel pickup truck with Colorado license plate 121XGO. Investigators believe Tanner may be armed with a handgun.

(credit: Larimer County Sheriff's Office)

(credit: Larimer County Sheriff’s Office)

Searchers exhausted their efforts at the Lon Hagler Reservoir and left the area about 11 a.m. Friday.

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(credit: Larimer County Sheriff's Office)

(credit: Larimer County Sheriff’s Office)

Anyone with information on the whereabouts of Tanner, his vehicle, or Ashley, is asked to call the Larimer County Sheriff’s Office at 970-498-5163.