Minor league baseball player's wife, baby, mother-in-law killed at their home: Sheriff

A minor league baseball player's wife, baby and mother-in-law were killed at their Virginia home, allegedly by another family member, authorities said.

Matthew Bernard, 18, was arrested on Tuesday afternoon on three counts of first-degree murder after he allegedly killed his mother, sister and baby nephew that morning at the family's home in Keeling, an unincorporated area near Virginia's southern border with North Carolina.

The victims were identified Wednesday as: Matthew Bernard's mother, 62-year-old Joan Bernard; Matthew Bernard's sister, 25-year-old Emily Bernard Bivens; and Matthew Bernard's nephew, 14-month-old Cullen Bivens.

A firearm was used in the crime and a 911 caller reported a shooting, but cause of death has not been confirmed, police said.

The victims were the mother-in-law, wife and child of Blake Bivens, a Double-A pitcher in the Tampa Bay Rays organization, Pittsylvania County Sheriff Mike Taylor said Wednesday.

A motive is not clear, Taylor said.

The Tampa Bay Rays said in a statement: "Blake Bivens, a pitcher with our Double-A affiliate, the Montgomery Biscuits, suffered a terrible family tragedy in southern Virginia. Our hearts are broken for Blake. We are grieving with him and will support him any way we can."

The Biscuits CEO and Managing Owner Lou DiBella said in a statement, "The Biscuits thoughts and prayers are with Blake and all those who have been impacted by this tragedy."

After the victims were discovered Tuesday morning, authorities launched a manhunt for Bernard, who was said to be armed and dangerous.

Danville Community College in Danville, Virginia, was under lockdown Tuesday as a "precautionary" measure after Bernard, who was a student there, was identified as the suspect, according to the Danville Police Department.

Pittsylvania County Public Schools also went on modified lockdown. Superintendent Mark Jones told ABC News all outside doors were locked and monitored, all classroom doors were locked and no students were allowed in hallways without a chaperone.

ABC affiliate WSET of Lynchburg, Virginia, was in a media staging area at the scene in Keeling Tuesday afternoon when suddenly Bernard, who wasn't wearing any clothes, ran out from a nearby wooded area and attacked a church groundskeeper then fled again.

"I saw a male, tall skinny male, with no clothes on running around," a woman told local reporters. "He took off running."

Authorities chased Bernard down the street and were able to apprehend the teen, who was taken to a local hospital for treatment, according to WSET.

It's not clear why he was found without clothes, the sheriff said Wednesday.

Bernard has not yet appeared in court.

ABC News' Darren Reynolds contributed to this report.