ALL RIGHT, MATT GUTMAN ON THIS TONIGHT, MATT, THANK YOU. >>> IN THE MEANTIME, TO BUFFALO, NEW YORK, TONIGHT, WHERE THE GUNMAN ACCUSED OF KILLING TEN PEOPLE AT THAT TOP'S SUPERMARKET BECAUSE THEY WERE BLACK, TONIGHT PLEADING GUILTY TO MURDER, ATTEMPTED MURDER, AND DOMESTIC TERRORISM MOTIVATED BY HATE. WHAT THE JUDGE DID TODAY IN THAT COURTROOM. READING EACH OF THE VICTIM'S NAMES. AND OF COURSE, WE REMEMBER THE TEN TWO DIED. THE YOUNGEST, 32, THE OLDEST, 86. AND THE YOUNG MAN WHO PLOTTED THIS, WHO DROVE SEVERAL HOURS TO GET TO THAT STORE AND WHO HAD VISITED THE STORE MULTIPLE TIMES BEFORE. STEPHANIE RAMOS IN BUFFALO. >> Reporter: TONIGHT, SIX MONTHS AFTER TEN BLACK PEOPLE WERE KILLED IN A RACIALLY MOTIVATED ATTACK AT A BUFFALO, NEW YORK, SUPERMARKET, THE GUNMAN PLEADING GUILTY. >> AND THAT IS WHAT WE GOT TODAY, WHICH WAS SWIFT JUSTICE. >> Reporter: THE STATE'S IDICTMENT AGAINST PAYTON GENDRON INCLUDES FIRST-DEGREE MURDER, ATTEMPTED MURDER, AND DOMESTIC TERRORISM MOTIVATED BY HATE, WHICH CARRIES A MANDATORY LIFE SENTENCE. IN THE COURTROOM, GENDRON REPLYING "YES" AND "GUILTY" AS THE JUDGE NAMED EACH VICTIM AND CHARGE. THE NOW 19-YEAR-OLD WAS ARMED WITH AN ILLEGALLY MODIFIED SEMI-AUTOMATIC RIFLE BACK IN MAY, WHEN HE DROVE MORE THAN THREE HOURS FROM HIS HOME TO TARGET THE PREDOMINANTLY BLACK NEIGHBORHOOD. OPENING FIRE IN THE PARKING LOT OF THE TOPS SUPERMARKET, THEN ENTERING THE STORE. GENDRON LIVESTREAMING THE CARNAGE FROM A CAMERA MOUNTED ON HIS HELMET. >> THIS DEFENDANT'S OWN HELMETED, MOUNTED VIDEO CAMERA, IT ESTABLISHES BEYOND ALL DOUBT THE GRUESOME FACTS OF THE DEFENDANT'S CONDUCT. >> Reporter: PROSECUTORS SAY HE DELIBERATELY PLANNED HIS ATTACK OVER SEVERAL MONTHS, EVEN VISITING THE SUPERMARKET TWICE. AND POSTED A DOCUMENT ONLINE SHORTLY BEFORE THE MASSACRE OUTLINING HOW HE PLANNED TO KILL AS MANY BLACK PEOPLE AS POSSIBLE. TONIGHT, HIS GUILTY PLEA LITTLE SOLACE FOR THE FAMILIES OF THE VICTIMS, INCLUDING GARNELL WHITFIELD, WHO LOST HIS 86-YEAR-OLD MOTHER RUTH. >> TO HEAR HOW SHE DIED, AND TO JUST IMAGINE WHAT SHE FACED IN THAT MOMENT, HAVING LIVED THE LIFE THAT SHE LIVED -- IT'S JUST TOUGH TO TAKE. >> Reporter: THE SHOOTER STILL FACES MORE THAN TWO DOZEN FEDERAL CHARGES. SOME OF WHICH CARRY THE POSSIBILITY OF THE DEATH PENALTY. AND TONIGHT, DAVID, WE ARE HEARING FROM HIS PARENTS WHO SAY THEIR HEARTS ARE BROKEN OVER THE DEVASTATION THEIR SON HAS CAUSED.