A Utah teen who was "known to run away" and living with his 15-year-old girlfriend on and off allegedly executed her inside her home with a single gunshot wound to the head at "close range," cops say.

Hezekiah Plummer, 16, is charged as an adult with first-degree murder , obstruction of justice and theft of a firearm in connection with the death of Chanelle Alvarez at her home in Ogden, according to a probable cause affidavit obtained by Law&Crime.

Plummer claimed that a "robbery" occurred at the residence early Saturday after he showed up around 1 a.m. and "claimed he had nowhere to stay," the affidavit alleges.

"The victim indicated it would be fine for Plummer to stay and he was allowed into the home," police say in the charging document.

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