(CNN) Authorities believe the phone of Matthew Thomas Bernard found near the scene of the triple homicide of his mother, sister and young nephew may contain "information identifying a motive for these shootings," a newly released Pittsylvania County search warrant says.

Bernard is accused of killing 62-year-old Joan Bernard, 25-year-old Emily Bivens, and 14-month-old Cullen Bivens, and was charged with three counts of first-degree murder and three counts of use of a firearm in the commission of a felony, according to CNN affiliate WSET.

Emily Bivens and Cullen Bivens are the wife and child of minor league baseball player Blake Bivens.

A state police investigator searched social media and found a post from Bernard indicating he was going through a divorce and to "never underestimate a Bernard," the warrant says.

Bernard's father confirmed to investigators the phone belonged to his son, according to the warrant.

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