A man has been sentenced to life in prison plus 20 years for a double murder in the South Side Washington Park neighborhood in 2010.

Samuel Gayden, 35, was previously found guilty of two counts of murder and one count of attempted murder, according to the Cook County state’s attorney’s office.

On Sept. 1, 2010, Marcus Marshall, 19; Shawntell Harris, 21, and a third person approached a liquor store in the 5700 block of South State Street, prosecutors said.

Marshall and the third person entered the store while Harris stayed outside, prosecutors said. Gayden entered the store, looked around, walked out and then waited outside.

A few minutes later, Harris entered the store, and Gayden followed, prosecutors said. Gayden opened fire, shooting Marshall and Harris.

Marshall and Harris were both killed, prosecutors said. The third person was not injured.

The shooting was caught by several surveillance cameras and Gayden was also identified by witnesses at the scene, prosecutors said. He was arrested a few days later, and the weapon was recovered.

While in custody at the Cook County Jail, Gayden allegedly made telephone calls and mailed letters attempting to have one of the witnesses murdered, prosecutors said. Those communications were intercepted by the sheriff’s office.

Judge Domenica Stephenson sentenced Gayden to life plus 20 years during a hearing Tuesday, according to the state’s attorney’s office.