Al Jazeera's Shihab Rattansi reports from Pittsburgh.
"The best thing we can do, no matter what age we are, is to go about living our lives proudly as Jews, and the essence of that is connecting to community", Jacobs said. A law enforcement source told CNN that investigators believe a Gab account that espoused anti-Semitic views belonged to Bowers.
Local television station KDKA cited police sources as saying Bowers walked into the building and yelled "all Jews must die".
Bowers had made many anti-Semitic posts online, including one early on Saturday.
Police said the suspect had three handguns and an assault-style rife at the shooting. After a shootout, he surrendered. No children were killed, authorities said.
Six people, including four police officers, were injured. Two of the six people injured were in critical condition. "It's incredible to see the amount of people who came out because I was feeling really alone and completely separated from the community that gave me my Jewish identity, and here I feel so uplifted and supported by completely random strangers I met on the Internet".
"The idea that that was shattered by this awful act of violence hit me to the core of my soul", Shanken says.More news: New iPad Pro to have rounded bezels, no Home button
Jones said agents are checking Bowers' social media accounts. It follows a spate of pipe bombs found mailed in recent days to prominent political figures, mostly Democrats, including former president Barack Obama.
"You have to talk to them in a way they understand", he said.
About half of the congregants at Beth Shalom do not drive on the Sabbath, he said.
Trump told reporters the killings might have been prevented if there had been an armed guard at the temple. "It's not easy being away but I was a big part of the Jewish community there, I worked at Jewish day camps and I know people at the JCC and they opened it and provided grief counselors - they're doing what they can in a time of tragedy".
President Frank-Walter Steinmeier voiced his dismay at the attack, which left 11 dead, in a condolence message to U.S. President Donald Trump.
Hissrich said extra patrols have been assigned to "sensitive locations around Pittsburgh", including at a vigil planned for Sunday night.
Once a final goal is hit, Celebrate Mercy said it will immediately transfer funds to the Islamic Center of Pittsburgh, which will work with Tree of Life to send the funds to victims to help with medical and funeral expenses.
"This is an very bad, terrible period for our Jewish community and especially for the families that have been affected", said Jeffrey Finkelstein, CEO of the Jewish Federation of Greater Pittsburgh.