Two teens have been charged as adults in the Valentine's Day strangulation of a 24-year-old guard in a western Nebraska jail.

Scotts Bluff County Attorney Doug Warner says in a news release Thursday that 16-year-old Guy Eagle Elk, of Lisco, has been charged as an adult with felony aiding and abetting assault. On Wednesday, 15-year-old Dylan Cardeilhac, of Torrington, Wyo., was charged as an adult with first-degree murder in the death of Amanda Baker.

An arrest affidavit says security video shows Cardeilhac talked Baker into checking something on his cell floor on Friday, then pounced on the guard when she turned her back. Authorities say the video shows Baker was strangled for more than 2 1/2 minutes.

Baker was taken to a local hospital, where she later died.