Police responding to an emergency call found the bodies of Hamilton, 50, and his 44-year-old girlfriend, Monica Jordan, in his Houston-area home, according to Yahoo Sports.
Authorities said it appeared Hamilton had been shot several times and Jordan died from a self-inflicted gunshot.
Hamilton and Jordan had a young child who was found safe and is now in the custody of Texas Child Protective Services.
Hamilton had played major league baseball for parts of 13 seasons, most notably with the Milwaukee Brewers in the 1990s, Yahoo Sports said.
Hamilton also played for the New York Mets, Colorado Rockies, San Francisco Giants and Texas Rangers, and was first player to get a hit in an interleague game in 1997.
“All of us at Major League Baseball are shocked and saddened by this tragedy,” Commissioner Rob Manfred said in a written statement released after Hamilton’s body was identified on Monday.
“[Darryl] was a talented and personable individual, and we were proud to call him a member of the Baseball Family,” Manfred said.
Hamilton also is survived by two sons from a prior marriage, Yahoo Sports said.
Hamilton batted .291 for his baseball career with 51 homeruns and 454 runs batted in, according to ESPN.com.
