A Port Richmond man has been sentenced to 25 to 50 years in prison after he pleaded guilty to third-degree murder in the stabbing death of his mother-in-law last summer.

Steven Estremera, 35, pleaded guilty Thursday and was sentenced immediately by Philadelphia Common Pleas Court Judge Benjamin Lerner. The sentence was reached in a plea agreement by Assistant District Attorney Joanne Pescatore and defense attorney Susan Ricci.

Estremera, also known as Estevan Gonzalez, was charged with the July 25 slaying of Marian Frew, 66, inside the home he shared with Frew's daughter in the 3400 block of Weikel Street.

At an earlier hearing, police detectives said Estremera had confessed to stabbing Frew repeatedly with a pair of scissors after they argued about her yelling at his children and she smacked him in the face.

Estremera initially told police he found Frew in the basement and implicated another man as her killer. When that suspect had an alibi, detectives turned to Estremera as the suspect.

Estremera, who also pleaded guilty to theft, receiving stolen property, possession of an instrument of crime, and filing false reports, made a brief statement apologizing to Frew's family before he was sentenced.

Contact staff writer Joseph A. Slobodzian at 215-854-2985 or jslobodzian@phillynews.com.