correction: This story was changed to correct the location of the incident and to reflect that the sentencing occurred in D.C. Superior Court, not federal court.

He had beaten his 81-year-old mother with his fist, a wooden stick and an iron in the summer at the apartment they shared in Northeast Washington after smoking crack earlier in the day. His mother later died, and a judge has sentenced the man — 52-year-old Derek Cook — to 20 years in prison.

Authorities said the killing occurred Aug. 12 when Cook was talking to his mother — Ann Alfredia Cook — in a bedroom at their apartment in the 5200 block of Fourth Street NE.

The two got into an argument about him smoking a cigarette inside, officials said. He started to hit his mother with a closed fist. She yelled for help. He also hit her with an iron and a wooden stick.

At the time, officials said, his mother was not armed and was in bed.

Cook had also admitted to smoking crack twice earlier that day, according to court documents.

When police arrived, Cook would let them only into the building and not into the apartment. Officers had to ram down the apartment door, and they found his mother severely injured. She was taken to a hospital, where she died later that night.

Cook had his mother's blood on his shirt when police arrived, according to court papers. He was arrested and has been in custody since.

In September, Cook pleaded guilty in D.C. Superior Court to second-degree murder while armed. Prosecutors said the plea called for an "agreed-upon sentence" of 20 years in prison. Cook was sentenced Friday.

Once he finishes his prison term, Cook will be placed on five years of supervised release.

This story has been updated. An earlier version gave the incorrect name of the court and the hundred block location of the incident. It is D.C. Superior Court and the incident happened in the 5200 block of 4th Street NE.