28 YO Gene Evin Atkins is named in several articles.
Here is one of the stories: https://www.nbclosangeles.com/news/local/Trader-Joes-Standoff-Suspects-Family-Reacts-488837201.html
Apparently he was in a feud with his grandmother over his girl friend.
'The next thing I do, I'm going to die doing it or I'm going to jail': Trader Joe's Standoff Suspect's Family Reacts
The suspect in the deadly Trader Joe's standoff on Saturday has been identified.
Twenty-eight-year-old Gene Atkins is accused shooting his grandmother and girlfriend, leading police on a car chase, then crashing running into a busy supermarket where he held dozens of people hostage in a standoff with the police.
One woman was killed in the shootout.
Charleo Egland, first cousin of the suspect, lives right next door to the house where Atkins shot his 78-year-old grandmother, Mary Madison, on Saturday. Atkins was living with his grandmother at the time of the attack, Egland said.
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There is more information at the link. A lot of it is opinions of neighbors/relatives.