A California father was stabbed to death in broad daylight while walking hand-in-hand with his 8-year-old son just moments after picking him up from school, cops say.

“The homicide was horrific,” said San Francisco Police Department interim Chief Paul Yep during a press conference Friday after the arrest of Robert Byrd II”s alleged killer.

“A father who was walking across the street with his son was fatally stabbed in the crosswalk after getting into an altercation with the suspect,” Yep told reporters. “Immediately after this incident occurred, our officers began a tireless investigation to identify and apprehend the suspect. We were relentless.”

Byrd had just done “school pickup” for his son at nearby Commodore Sloat Elementary School in San Francisco on Wednesday when he was attacked during an argument with another man, police officials say. “There were words that were exchanged, and other people heard the commotion and what was happening, and the perpetrator stabbed the victim and ran away,” San Francisco District 7 Supervisor Myrna Melgar told local ABC affiliate KGO on Wednesday after the slaying.

Cops have not released a name or motive for the suspect, who was reportedly behind bars over the weekend, but they have said he was a resident who lived nearby. Investigators used automated license plate readers, surveillance cameras and a drone to find and capture the man, along with eyewitness accounts.

“Many of our officers haven’t slept in a couple days,” SFPD official Thomas Maguire told reporters on Friday. “They worked around the clock. With community cooperation and with utilizations of technology and a major deployment of our police personnel, we were able to follow leads that led us to Tuolumne County, and we made a safe arrest.”

Officials described Byrd’s death as “particularly disturbing to the community and to the parents and students” of the San Francisco Unified School District. Superintendent Maria Su said Friday that it was a “horrific, horrific tragedy” that SFUSD had “never experienced at this level” before.

“A kid shouldn’t lose his father,” resident Trish Lethin told KGO. “But then to have to see him die or be with him when he is dying, that is not okay.”

Teresa Agustin, a parent whose child attends Commodore, wrote on Facebook Sunday that when she would pick her son up from school, Byrd “was always there early waiting for his own son” to come out. “He offered a welcoming smile and I’ve always waved back,” Agustin said, sharing a GoFundMe that was started for Byrd’s family.

In the description, Byrd is described as a devoted father whose “greatest love was his son, who was holding his hand in the moments before this tragedy occurred,” according to the school’s Parent Club Organization, which launched the GoFundMe. “This senseless act of violence has left us all deeply shocked and heartbroken,” the group said.

Local prosecutors are currently reviewing evidence to determine what charges are warranted for Byrd’s alleged killer. San Francisco District Attorney Brooke Jenkins said Friday that her office will announce charges in the coming days.

“We do ask for your patience in allowing us to review all of the evidence that still needs to be collected as well as what has already been collected,” Jenkins told reporters. “We do still have outstanding witness interviews that need to happen so that we can make a comprehensive decision about what to do going forward.”