Law enforcement officials say a man suspected of leaving a backpack bomb outside a Colorado police station was spotted on surveillance video from a store where he bought a cellphone used in the device.

Two officials with knowledge of the investigation tell The Associated Press that 64-year-old David Michael Ansberry was noticeable because he is 3 feet 6 inches tall.

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The officials spoke on condition of anonymity because they weren't authorized to publicly discuss the case.

One of the officials says the device was designed to be remotely detonated using a cellphone but failed.

Ansberry was arrested over the weekend in Chicago.

A detective found the device in a backpack Oct. 11 and brought it into the Nederland police station, believing it was lost property. It was eventually detonated in a parking lot.

- Associated Press writers Sadie Gurman in Denver and Michael Tarm in Chicago