Minor league baseball pitcher Blake Bivens shared a heartbreaking Instagram post honoring his wife, son and mother-in-law Thursday night. It's his first public statement since all three were found dead in Virginia earlier this week.

"Two days ago my heart was turned to ash," Bivens wrote on Instagram, sharing photos of his slain family members. "My life as I knew it is destroyed."

His wife, 25-year-old Emily Bernard Bivens, 14-month-old son Cullen Micah Bivens, and Emily's mom, Joan Denise Jefferson Bernard, 62, were found dead by police Tuesday morning. Authorities arrested Matthew Thomas Bernard, Emily's brother, and charged him with three counts of first-degree murder.

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"The pain my family and I feel is unbearable and cannot be put into words," Bivens wrote. "I shake and tremble at the thought of our future without them."

In his Instagram post, Bivens addressed each of his family members individually, sharing parting words to them.

"Emily, my sweetheart, you are the best wife and mother this world has ever seen," he said. "Your love and kindness changed countless lives, including mine."

Addressing Cullen, Bivens said his life is forever changed because of his son.

"I can't breathe without you here," he said. "I finally understood what love was when you were born and I would have done anything for you."

He called his mother-in-law "the best Nana this world has ever seen."

Bivens concluded by thanking his friends and family, as well as his baseball community for their support.

Bivens, 24, plays for the Tampa Bay Rays' Double-A affiliate, the Montgomery Biscuits. CBS Sports reports he was a fourth-round draft pick in 2014.

"Our hearts are broken for Blake," the Rays said in a statement after news broke of the murders.

"I've been blessed beyond belief," Bivens wrote on Instagram. "I'm not sure what is next for me, but I do know God has a plan even though I can't see it."

Investigators are still trying to determine a motive in the killings, The Associated Press reports. Bernard, 18, was captured running naked through the town of Chatham, Virginia, after a manhunt involving nearly 100 officers, authorities said Wednesday.

Bernard was taken to the hospital after banging his head against the cage in a police vehicle. He was moved to jail Wednesday and is being kept on suicide watch, Pittsylvania County Sheriff Michael Taylor said at a news conference.

A firearm was "involved in the incident," according to Taylor, but details about how the victims died have not been released.