Police are warning about the dangers of “bank jugging,” after a spate of such robberies across California.

During these types of thefts, assailants watch bank patrons withdraw money from branches or ATMs, follow them, then rob them off-site, according to law enforcement.

A Los Angeles man, who gave his name as ‘Robert’, told KTLA he was the victim of one such theft on July 7, after he withdrew thousands in cash from a Bank of America branch in the Pico-Robertson neighborhood.

“I had it in an envelope, a few thousand dollars,” Robert told KTLA. “It’s a lot of money. I’m not rich. I work hard.”

Surveillance video shows a man breaking into Robert’s car and taking the cash while Robert was in a grocery store.

“These guys definitely were inside the Bank of America,” Robert added. “They’re looking for somebody and it happened to be me.”

Two days later, a man in Fontana had his car robbed at a gas station under similar circumstances, according to police there.

“While he was away from his vehicle, a late-model black Hyundai Tucson pulled up next to it. A tall, slender male adult exited the front passenger seat of the Hyundai, smashed the victim’s window, and stole the cash,” police spokesperson Officer Daniel Romero told the Press-Enterprise newspaper.

The thief then fled, in a car driven by a woman, the officer said.

“It is a classic case of jugging,” Romero added, calling it an “an escalating criminal activity.”

Earlier this month, police in Orange County arrested three people suspected of bank jugging.

The FBI warned about bank jugging last year.

“These assailants are brazenly targeting bank and ATM customers, posing a significant risk to the public of both physical and financial harm,” FBI Baltimore Special Agent in Charge William J. DelBagno said at the time.

To avoid bank jugging risks, law enforcement advise people to be aware of their surroundings, report suspicious activity, conceal cash withdrawals, vary their banking habits, and avoid unnecessary stops after pulling large sums of money.