MARTINEZ -- A 25-year-old Pinole man with "significant mental health issues" was charged with murder Tuesday for killing his grandmother and uncle with a butcher knife, a prosecutor said.

Jeffrey Flores is expected to be arraigned in a Richmond courtroom Wednesday morning on two counts of murder with use of a knife in the Friday slayings of Nona Jean Flores, 76, and her 54-year-old son, Tony Flores. The defendant is also charged with a multiple victims special circumstance allegation that makes him eligible for the death penalty or life in prison without the possibility of parole.

Deputy district attorney Mary Knox said it is unclear why Jeffrey Flores attacked the victims, but investigators believe that his mental health issues played a role.

Flores called police to the 1100 block of Tara Hills Drive about 2:30 a.m. Friday and reported that he heard someone in the home he shared with the victims, and his sister and her family.

Officers arrived just minutes later to find Nona and Tony Flores dead in separate bedrooms, each with "devastating wounds to their necks," Knox said. A butcher knife was still lodged in one of the victims.

Flores is being jailed without bail.

Contact Malaika Fraley at 925-234-1684. Follow her at Twitter.com/malaikafraley.