A 19-year-old man accused of opening fire on Sabbath worshippers in a deadly shooting rampage at a southern California synagogue is believed to have acted alone, without help from any organized group, authorities said on Sunday.

Police say the gunman walked into the suburban San Diego synagogue late on Saturday morning, the last day of the week-long Jewish holiday of Passover, and killed one woman and wounded three other people inside, using an assault-style rifle.

The suspect, John Earnest, then fled in a car before calling police to hand himself in, according to authorities. 

“We believe he acted alone and without outside support in carrying out the attack,” San Diego County Sheriff Bill Gore said in a statement.

The suspect, who is also under investigation for a mosque arson, has been booked into custody on one count of murder in the first degree and three counts of attempted murder in the first degree, Gore said.

At an emotional news conference on Sunday, Rabbi Yisroel Goldstein choked back tears as he spoke of the slain victim, Lori Kaye, whom he had known for 25 years.

“She was a pioneer member from our congregation,” he said, his left arm in a sling and his right hand bandaged. “Lori had unconditional love for all.”

Goldstein had surgery at a hospital after his right index finger was blown away by the gunman. He recounted how after he saw the carnage, he grabbed a prayer shawl, wrapped it around his bloody hands and addressed the congregation.

After the shooting, the suspect fled in a car, escaping an off-duty U.S. Border Patrol agent who shot at the getaway vehicle but missed the suspect. The suspect pulled over and surrendered to police officers a short time later.

The teenage suspect, who had no prior criminal record, is the apparent author of a “manifesto” who claimed to have set a nearby mosque on fire last month and professed drawing inspiration from the gunman who killed nearly 50 people at two mosques in New Zealand.

The Passover violence came amid an upsurge in reports of anti-Semitism nationwide and abroad and followed a recent spate of deadly attacks on places of worship around the world.

Suicide bombings during Easter Sunday services at several churches in Sri Lanka killed more than 250 people. A gunman who opened fire at two mosques in Christchurch, New Zealand, on March 15 left 49 people dead and more than 40 wounded, some as they knelt in prayer.

(Cover: A San Diego County Sheriff secures the scene of a shooting at the Congregation Chabad Synagogue in Poway, north of San Diego, California, April 27, 2019. /Reuters Photo)