IOWA CITY – Michael Swanson, who killed two convenience store workers in 2010 and was convicted in 2011, will serve an additional 25 years after pleading guilty to attempted murder.

Swanson, 21, made the guilty plea Tuesday to slashing a fellow inmate with a knife at the Iowa Medical and Classification Center in Coralville.

A second inmate, Michael Ivester, 34, pleaded guilty to attempted murder in late October.

On Nov. 15, 2010, Swanson, then 17 years old, shot Sheila Myers at a Humboldt convenience store. Earlier in the evening, he shot Vicky Bowman-Hall at a convenience store in Algona.

Both women were survived by husbands and children.

Swanson was convicted of first-degree murder and first-degree robbery for killing Myers. He shot Myers in the face with a .40-caliber Beretta handgun and left the Kum & Go store with $31 and some cigarettes.

He received a life sentence for that murder.

Swanson pleaded guilty to first-degree murder and first-degree robbery for Bowman-Hall’s death.

He admitted during his plea hearing that he walked into the Crossroads convenience store on the night of her death armed and shot Bowman-Hall with the intention of killing her.

Swanson received a life sentence for that murder.

In 2013, Gov. Terry Branstad commuted the life sentences of 38 Iowa inmates convicted as juveniles, including Swanson, to terms of 60 years in prison before they could be eligible for parole.

That order came following a 2012 United States Supreme Court ruling that threw out automatic life sentences for juveniles.

A re-sentencing hearing for Swanson has been continued indefinitely due to the attempted murder case, according to Iowa Courts Online.