By Dan Whitcomb

LOS ANGELES (Reuters) - A man who fatally shot a security screener and wounded three other people at a Los Angeles International Airport terminal in 2013 pleaded guilty on Tuesday to federal charges under an agreement with prosecutors that spares him the death penalty.

Paul Ciancia, 26, entered his guilty plea to murder of a federal officer and 10 other criminal counts during a hearing in federal court in Los Angeles, said Thom Mrozek, a spokesman for the U.S. Attorney's Office.

Ciancia is expected to face a sentence of life in prison without the possibility of parole when he is sentenced on Nov. 7.

"The guilty pleas entered in court today will hopefully bring some justice to the victims of this horrific attack that senselessly ended the life of a federal officer and injured several others,” U.S. Attorney Eileen Decker said in a written statement.

Federal prosecutors said last year they intended to seek the death penalty for Ciancia if the case went to trial, citing what they said was his substantial planning and premeditation ahead of the crime and its impact on the victims.

They agreed not to seek the death penalty under a plea agreement that avoided a lengthy trial.

Authorities say Ciancia walked into Terminal 3 of the second-busiest U.S. airport carrying a semi-automatic rifle and opened fire, killing Gerardo Hernandez, 53, an agent for the U.S. Transportation Security Administration, as he stood at the entrance to a security checkpoint.Hernandez was the first TSA officer killed in the line of duty since the agency was created following the Sept. 11, 2001, suicide hijacking attacks on the United States.

Federal authorities have said that Ciancia, from New Jersey, had set out to target TSA employees.

Investigators said in a criminal complaint they found a handwritten letter signed by Ciancia in his bag that addressed TSA officials, writing that he wanted to "instill fear in your traitorous minds."

According to the plea agreement, Ciancia admitted purchasing a semi-automatic rifle, 500 rounds of ammunition and 10 magazines in preparation for the attack.

(Reporting by Dan Whitcomb; Editing by Peter Cooney)