A California police union is blaming a city's brutal day of violence on low staffing and morale.

On what Oakland's police union is calling "Bloody Monday," four people were killed, and multiple people injured following several shootings and a stabbing. The union says officers have been leaving the department because of the defund the police movement, KPIX-TV reports.

“Stop the attrition," Barry Donelan, the union president, said in a statement. "We’re losing 10 a month, and (we need to) provide these officers a sense of value and appreciation that they deserve as the dedicated public servants that they are. Last night was extremely taxing to those who were on duty."