The crashes occurred just 25 yards apart on Loma Vista Drive, the chief said.
"I drove out here myself and I still didn't believe it," Beck told reporters Friday. "It is just too horrific for words."
The name of the detective -- who was off-duty at the time of the crash - has not been released pending notification of family. Beck said the officer had been with the department for more than 25 years and "regularly traveled" Loma Vista for a second job.
"I have known him for several decades," the chief said. "He is a fine family man. He will be sorely missed."
The detective was killed when a cement truck struck his pickup shortly before 2 p.m. in the 1000 block of Loma Vista Drive, according to Beverly Hills police Sgt. Mark Subin. The driver of the cement truck was taken to a nearby hospital in serious condition.
Initial information indicated the cement truck was heading south on Loma Vista when it lost control, crossed double yellow lines and struck the pickup, police said Friday. The cause of the crash remains under investigation.
The mangled vehicles were marked off by police tape by late Friday afternoon as police officers and firefighters lined the road. They saluted as the officer's flag-draped body was rolled to a coroner's van.
Two months ago, LAPD Officer Nicholas Lee was killed when an out-of-control dump truck struck his patrol car. Skid marks from that crash could still be seen on the pavement Friday.
The crash marked the third time in recent months that a large truck lost control on the roadway; the most recent occurred a week ago when a cement truck struck several parked cars. That driver suffered minor injuries.
Beverly Hills police Chief David Snowden said Friday that a 30-day moratorium had been placed on all heavy trucks traveling the street. Trucks coming in and out of the area will also be weighed, he said.
"We are devastated by the accident and mourn with the family of the detective who died," Beverly Hills Mayor Lili Bosse said in a statement.
The road is lined with signs warning drivers of large trucks to be wary of the steep incline, to obey speed limits and even has a runaway truck ramp at the bottom. But the street is also home to multimillion-dollar mansions that are seemingly constantly under construction.
In a statement, Beverly Hills officials said they were "aware of the concerns from the community" regarding commercial vehicles traveling in the area. City officials said police had "significantly" stepped up enforcement efforts since January, including two electronic radar signs.
"This is a critical public safety issue which the Beverly Hills Police Department and other city departments are aggressively working together to mitigate future accidents," the statement read.
But many residents have expressed outrage over what they describe as an unsafe road.
Cheri Shankar, who has lived in the 1900 block of Loma Vista Drive for about eight years, said several large trucks use the street each day. Loma Vista can be difficult even for smaller vehicles, she said. Driving down, "you don't have to touch the accelerator," she said. "You have to ride your brake."
Shankar was puzzled by the uptick in crashes -- before March, she said, she had not been aware of any other incidents. She's since written to the mayor, urging action.
"It's bizarre," she said. "This cannot be a coincidence. I am really scared to drive on my street now."
The crash also marked the fourth time in two months that an LAPD officer was killed in a traffic incident. The three other officers killed were on duty at the time.
Lee died first, when the dump truck struck his cruiser on Loma Vista Drive on March 7.
Last month, motorcycle Officer Chris Cortijo died from injuries he suffered while he was waiting at a red light and was hit from behind by a woman suspected of being under the influence of drugs.
And on Saturday, LAPD Officer Roberto Sanchez was killed and another officer injured when their patrol vehicle was struck by an SUV in Harbor City. The driver of the SUV has been charged with murder in Sanchez's death; his funeral services are scheduled for Wednesday.