Former Tampa Bay Rays prospect Brandon Martin has been convicted of murdering three men with a baseball bat at his family’s Corona home.

After four hours of deliberations, a Riverside County Superior Court jury found Martin guilty of first-degree murder Wednesday in the Sept. 17, 2015, deaths of his father, Michael Martin, uncle Ricky Andersen and alarm installer Barry Swanson.

In addition to three murder counts, the jury convicted Martin of evading arrest, resisting arrest, stealing an auto and injuring a police dog.

The jury is scheduled to start hearing testimony Monday in the sentencing phase. Prosecutors are seeking the death penalty.

The Rays picked Martin from Corona Santiago High with the 38th overall selection in the 2011 draft. The shortstop received an $860,000 signing bonus and drew on-field comparisons to New York Yankees legend Derek Jeter.

But Martin’s behavior grew erratic in the years after being drafted, according to court records and interviews with friends, including punching his father in the face and putting his mother in a headlock.

The Rays released Martin in early 2015. He hadn’t played in a game in more than a year.

Two days before the murders, Martin was placed on a mental-health hold in Riverside after he admitted to Corona police officers that he choked his mother and threatened her with scissors.

The family was having a security system installed on the day of the murders to protect them.

The murder weapon, a black baseball bat, was engraved with Martin’s name and left at the scene.

When authorities apprehended Martin the next day, police records allege he body-slammed a police dog and fought officers.

Martin, 27, has been jailed without bail in Riverside since his arrest.

This story originally appeared in Los Angeles Times.