Deep sympathy to the family members and friends of the congregant who was killed by the 19 year old young man; from indications thus far it appears he thought Jews are immigrants who should be wiped out. The anti-immigrant sentiments that rise to the point of hatred even/especially in the highest levels of political “leadership” drive many well-informed and ill-informed Americans to make all those with skin hues different from theirs speaking languages they don’t understand enemies to drive away or to kill.
This young man evidently decided several dead Jews (a filled synagogue on the last day of the vitally important Passover) would help the “true American” cause. And he will be praised for his actions by more than a few. No religious group that promotes prejudice deserves to survive.