Four code-enforcement trucks were torched in the Hemet City Hall parking lot Tuesday, in a brazen attack that police believe is part of a shadowy but relentless campaign of violence against them.

"We are assuming, because of the timing, that this is related to the other three attacks on our gang task force," said Lt. Duane Wisehart, standing near the crime scene off busy Florida Avenue, two blocks from the police station. "We are looking mostly at gangs as suspects because our task force is being targeted."

Riverside County and state officials have offered a $200,000 reward for the capture of those behind the recent attacks on a gang task force. (Irfan Khan / Los Angeles Times)

The truck engines were set alight about 11:30 p.m. A man spotted nearby was questioned but later released. Video from surveillance cameras is being reviewed by investigators.

"Every day we worry about what's next," Wisehart said.

There have been three attacks on the Hemet-San Jacinto Gang Task Force since December.

In the first, someone scaled the roof of the unmarked task force headquarters and redirected a natural gas pipeline inside, filling the place with fumes; a single spark could have triggered an explosion. In February, a homemade zip gun was planted in the iron gate of the task force parking lot. When an officer opened the gate to go in, the gun fired a single bullet, missing him by a few inches.

In the third incident, two weeks ago, a gang enforcement officer found a suspicious device attached to his unmarked vehicle. Police determined it was dangerous.

And last Friday, someone called 911 and said that a police car would be blown up in the next two days as revenge for a law-enforcement sweep of a local gang.

Atty. Gen. Jerry Brown visited the area last week and joined with Riverside County Dist. Atty. Rod Pacheco in offering a $200,000 reward for the capture of those behind the attacks. Brown called it "urban terrorism."

A day before his visit, authorities in Riverside County, Arizona, Utah and Nevada launched a massive crackdown on the Vagos motorcycle gang, which has a major presence in Hemet and a history of violence toward police. They arrested 30 members throughout Riverside County on charges that include possession of drugs and weapons.

Pacheco has been careful not to directly name members of the Vagos gang as suspects in the assaults, but he has repeatedly pointed out how skilled the gang is at infiltrating police departments and keeping officers under surveillance.

He has called Hemet "ground zero" in the county's battle against gangs, saying 2,000 gang members reside in the area.

On Wednesday, police Chief Richard Dana looked weary after spending the entire night at the crime scene.

"I wasn't going to leave my men out there alone," he said. "Maybe this was an attempt to get them out there and attack again."

Members of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives used dogs to sniff out evidence. The FBI has also been involved.

Down the street from the crime scene, new barricades and fences were going up around the police station, giving parts of it the look of a fortress.

Surveillance has been beefed up and anyone carrying a backpack or loitering outside can expect to be questioned, police said. A block away, the gang task force offices sit empty, the officers having moved to an undisclosed location.

Wisehart said he didn't have a damage estimate for the pickup trucks, but added, "It looks like a total loss." Code enforcement, he said, has just two vehicles left.

He said the collective effect of the incidents has been to keep police on their toes.

"They are being more cautious," he said. "But there is also a sense of determination that they really want these people caught."