The man accused of fatally stabbing four people and wounding two others in a crime spree Wednesday that spanned two hours and two Southern California cities is a documented gang member, police said Thursday.

But, officials said, it is not entirely clear what motivated the suspect, Zachary Castaneda, 33, to go on the attack Wednesday in Garden Grove and Santa Ana.

"We just know that this was a random act of violence, and the guy unleashed evil," in the neighboring Orange County cities, Garden Grove police Lt. Carl Whitney said.

Castaneda, who was arrested near a Santa Ana 7-Eleven where a security guard was fatally stabbed, was combative with police Wednesday night, Whitney said.

"He remained violent with us through the night. He never told us why he did this," Whitney said at a news conference. "We know at three locations he robbed people for cash — we don’t know if the motive behind this was purely for robbery."

Prosecutors have not filed charges against Castaneda, but an official with the Orange County District Attorney’s Office said that prosecutors could seek the death penalty.

It was not clear from online records if he had an attorney who could speak on his behalf Thursday night. Castaneda is expected to be arraigned Friday.

Garden Grove Police Chief Tom DaRé said that without the work of the police and the undercover detectives who spotted the suspect’s car at the 7-Eleven, more people would have been attacked or killed in the "chaotic event."

But DaRé also said that Castaneda, who had previously been convicted of possession of methamphetamine for sales while armed with an assault rifle, should never have been free.

"This person should have been in prison and not allowed to be in our community, committing these violent acts," DaRé said.

This photo shows a booking mug shot of Zachary Castaneda posted outside of the Garden Grove Police Department headquarters in Garden Grove, Calif., Thursday, on Aug. 8, 2019. Marcio Jose Sanchez / AP

Online court records show Castaneda pleaded guilty to possession of a controlled substance while armed with a firearm, possession of an assault weapon and other counts in May 2014.

The Associated Press reported that he served about two years of a four-year sentence and was released on probation in January 2016, according to the California Department of Corrections and Rehabilitation. Castaneda was arrested last month on drug charges and is accused of having a concealed dagger while on bail for a June arrest for street gang vandalism.

In Wednesday's violent rampage, Castaneda burglarized an apartment about 4 p.m., then later stabbed the two occupants after a confrontation, police said.

The two men killed at the apartment were identified as roommates, one of whom was a 62-year-old man.

One owned a "sword or knife collection" that was stolen, but police don’t know if any of those weapons were used in the crime spree, which started just after 4 p.m.

Castaneda then allegedly attacked a 54-year-old woman working at an insurance business, stabbing her multiple times without provocation. Officials said he later attacked a 44-year-old man pumping gas at a Chevron station with two machetes, nearly severing his nose. Both of thoese victims are expected to survive, Whitney said.

Undercover officers found the suspect’s Mercedes at the Santa Ana 7-Eleven, saw Castaneda outside the store with a knife and the security guard’s gun, ordered him to drop the weapons and then arrested the man, Whitney said.

A private security car is seen in front of the 7-eleven shop in Santa Ana, California on Aug. 8, 2019 where a security guard was fatally stabbed. Apu Gomes / AFP - Getty Images

Police attempted life-saving measures on the security guard who had been stabbed, but he died at a hospital, Whitney said. Before the attack at the gas station, Castaneda allegedly stabbed a customer at a Subway restaurant across the street, and he also died from his injuries.

Police on Thursday released surveillance video that captured the attack at the insurance office. It shows a man in a hooded sweatshirt approach a woman at her desk before pulling out what appears to be two knives and repeatedly stabbing her. The woman then positions a chair between her and the attacker and crouches near a wall.

"Without provocation, he stabs her multiple times," Whitney said.

Whitney said that an employee at a check-cashing business in the same office then “threw cash at the suspect” and Castaneda fled. Whitney said the wounded woman has undergone surgery and is expected to survive, but said he was told one of the wounds narrowly missed her heart.

Castaneda, who was arrested just before 6:30 p.m. Wednesady, is also accused of robbing two other businesses Wednesday, but no one was hurt in either incident.