(CNN) -- As investigators search for answers in the deadly shooting at a California synagogue, police are looking into a possible link between the suspected gunman and a fire at a nearby mosque.
One person was killed and at least three others wounded in a shooting Saturday at Congregation Chabad in Poway, about 22 miles north of San Diego, according to authorities.
The San Diego Sheriff's Department said it assigned deputies to religious centers throughout the weekend. While security has been heightened, authorities said it is not indicative of a greater threat.
"We encourage our communities to continue with scheduled events and other activities as normal," the department said in a statement. "The suspect in the Poway incident today has been captured and we believe he acted alone."
The suspect in custody has been identified as John Earnest, a 19-year-old student at California State University San Marcos.
He was booked into San Diego Central Jail early Sunday on one count of first-degree murder and three counts of first-degree attempted murder, according to the San Diego Sheriff's Inmate Website.
Authorities are investigating whether he is connected to an arson attack at a mosque in nearby Escondido last month, San Diego County Sheriff Bill Gore said.
The San Diego Sheriff's Department is executing search warrants at the home and car of the suspect as well as at the synagogue, according to a release from the agency.
What happened in the synagogue
Gore told reporters that the gunman was armed with an "AR-type assault weapon." A witness told CNN affiliate KGTV there were six or seven shots followed by screams and then another volley of shots. The witness said a wounded rabbi tried to calm the gunman and members of the congregation.
Authorities said an off-duty Border Patrol agent, who Gore thinks is a security guard, fired at the shooter as he was fleeing the scene. He didn't hit the suspect, but Gore said it appears he hit the suspect's car.
It is unclear why the suspect fled but it is possible his gun might have malfunctioned, the sheriff added.
The suspect fled the scene and called 911 to say he was involved and give his location, San Diego Police Chief David Nisleit said. A San Diego K-9 officer arrived and the shooter surrendered without incident, he said.
Gore said the suspect was being interviewed by detectives and the FBI.
In an interview with CNN's Nick Watt, Poway Mayor Steve Vaus said preparations that the congregation put in place following the shooting at the Tree of Life Synagogue in Pittsburgh last fall likely prevented more deaths on Saturday.
"Just a few days after the Tree of Life Massacre in Pittsburgh we came together here with the Rabbi and his congregants ... and not only memorialized the victims of Pittsburgh but we talked about how to minimize future tragedies," Vaus said. "And I have no doubt that saved lives yesterday."
An open letter may give insight
Gore did not comment on a motive, but authorities are aware of an open letter posted online purportedly by the suspect, Gore said in a news conference.
Detectives are "collecting digital evidence" and are in the process of reviewing the online content "to determine its validity and authenticity," the sheriff said.
CNN has read through an open letter posted to the anonymous message board 8chan before the shooting.
In the posting, someone identifying as Earnest references killing Jewish people without making actual reference to Poway, San Diego or the synagogue involved in the shooting.
The letter writer talks about planning the attack and references other attacks on houses of worship, including the attack on the synagogue in Pittsburgh and the Christchurch mosque shootings in New Zealand.
The writer also talks about his disdain for Jews and claims responsibility for a mosque fire in Escondido last month -- a week and a half after the attacks in Christchurch. Graffiti referencing the New Zealand mass shooting was discovered at the scene of that fire.
The open letter is structured in a similar fashion to the manifesto linked to Christchurch attack suspect Brenton Tarrant, including a question-and-answer section in which the writer refers to questions he comes up with about his character, political affiliation and motivation for carrying out the alleged shooting.
The Palomar Medical Center received four patients from the shooting, according to a trauma surgeon. One patient died at the hospital, Dr. Michael Katz said. By Sunday morning all of the injured had been discharged from the hospital, according to a spokesman.
An employee of the synagogue identified the woman killed as Lori Kaye, 60.
"The other three victims are doing well with their injuries," Katz said.
A 34-year-old man and a girl had shrapnel injuries. The man was identified by congregation member Roneet Lev as Almog Peretz, who was visiting from Israel.
Peretz told CNN Sunday in an interview he is "slowly, slowly improving," and recounted seeing the shooter standing by the door of the synagogue in the lobby when he opened fire, in case he needed to run.
Peretz believes he was wounded on the second or third shot. "He didn't yell anything specifically at (me)," he said. "He was across the way. He was shooting at me from across the room. I saw him staring at me."
The girl was wounded in a leg and in the face, and was transferred to a children's hospital. Her age was originally reported as 9, but Noya told CNN she is 8.
Her father, Israel Dahan, said Peretz is her uncle and was injured protecting her.
A 57-year-old rabbi who was shot has been identified as Rabbi Yisroel Goldstein.
In a phone interview with CNN's Brian Stelter Sunday morning, Goldstein said he "met the terrorist face to face. Our eyes locked, and he aimed at me and miraculously I was able to just survive using my fingers.
Doctors were unable to save the index finger on his right hand, Goldstein said, and it remains to be seen if they will be able to save the finger from his left hand.
Goldstein also said that Kaye -- who he called a "long-time member" -- was "shot point-blank."
Congregation member Minoo Anvari, who said her husband witnessed the shooting, said the rabbi called for unity and prayed for peace even after getting shot.
"Rabbi said, 'We are united,'" said Anvari, a refugee from Iran.
As the rabbi was rolled into surgery, Lev said he told her that Kaye was killed after stepping between him and the gunman.
"She didn't die a senseless death," Lev said of her friend. "She died advertising the problem we have with anti-Semitism and to bring good to this world because she is the best person I've ever known."
The shooting happened at 11:23 a.m. (2:23 p.m. ET). The synagogue's Facebook page said a Passover celebration was scheduled for 11 a.m.
Passover, one of the holiest Jewish celebrations of the year, ended Saturday.
"As Americans, we can't cower in the face of the senseless hate that is antisemitism," Goldstein said in a statement Sunday. "This horrific event must also raise alarm and concern for the safety of all places of worship and our government needs to continue to step up and help properly secure them.
"I pray for healing during this time of pain and grief, and ask that we all do something to add more light to combat this evil darkness, through acts of compassion and loving kindness."
'Yet another wake-up call'
President Donald Trump, speaking outside the White House on Saturday, told reporters that the shooting "looks like a hate crime."
Many groups condemned the attack.
"Moving forward this must serve as yet another wake-up call that antisemitism is a growing and deadly menace," the Holocaust Memorial Museum said in a statement. "All Americans must unequivocally condemn it and confront it in wherever it appears."
Jonathan Greenblatt, CEO of the Anti-Defamation League, urged all religions to stand together in solidarity.
"All of these attacks on these sacred spaces represent a violation of our values that we as Americans hold dear: Values of decency, tolerance and respect. Whether or not you go to a church or a synagogue or a mosque, it's standing together with your fellow Americans that matters most," he said.
Abbas Barzegar, director of research and advocacy for the Council on American-Islamic Relations, applauded religious leaders and urged them to do more.
"Faith leaders around the world are already doing a great job working together to overcome the shared challenge of extremism," Barzegar said.
"They simply need to tell their story more and better, and most importantly spread that message down to the local community level and challenge hate in their own ranks."
Correction: A previous version of this story misstated the age of Noya Dahan.
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