And then all chaos broke out.
A man suddenly drove a car through the consulate visa office on Geary Boulevard shortly after 3pm, officials said.
Police opened fire on the vehicle, striking the driver.
The man, who was identified as 31-year-old Zhanyuan Yang, was taken to hospital where he was pronounced dead.
No one else was reported as injured in the incident.
San Francisco police are now working with the US State Department to investigate the incident, with many questions still unanswered about what Mr Yang’s motives may have been.
Here’s what we know so far:
A driver reportedly sped into the Chinese consulate visa office in San Francisco shortly after 3pm on Monday afternoon, according to authorities.
Witness Sergii Molchanov told The San Francisco Standard that the driver shouted “Where’s the CCP (Chinese Communist Party)?” as he got out of the car.
Security guards then approached the bleeding man, according to Mr Molchanov, and held his arms back before police arrived.
Police said that officers arrived on the scene moments later and found a blue Honda car had come to rest inside the building.
Officers entered the building and shot the driver after they “made contact” with the individual, police San Francisco Police Sgt Kathryn Winters said.
Multiple gunshots were fired during the incident, according to witnesses, before a bloodied man was loaded into an ambulance and driven from the scene.
The driver later died at hospital.
Bomb squad technicians and an explosives-sniffing dog attended the scene, The San Francisco Standard reported.
Mr Molchanov described the incident as “terrifying” and “shocking”.
“I’ve seen this on TV and to witness it in real life is quite different. People were terrified ... I was quite shocked with all that and am still processing that,” he said.
San Francisco Police said it is currently unclear how many people were inside the building at the time of the crash.
Police advised people to avoid the entrance to the visa office at Laguna Street and Geary Boulevard, which remained covered in a white plastic sheet on Monday evening, according to The San Francisco Chronicle.
Who is the man shot by police?
Police said the man has been identified as 31-year-old Zhanyuan Yang.
No additional information was released.
Yang was reportedly waving a knife in close proximity to officers just moments before he was shot by the police, according to local media.
Investigators say they have recovered a crossbow from the scene and an unnamed White House source told the Associated Press that it is believed the driver was “acting with malign intent.”
The licence plate of the car Yang crashed into the visa office was registered under a different name, authorities said.
Police said they did not know the motive behind smashing the car into the consulate, which is in a residential neighbourhood next to a major street.
Yang was described as a “very reserved” person by his roommate. He had a cache of replica firearms at his Inner Sunset home along with a book about political assassinations, The San Francisco Standard reported.
He reportedly had five handguns in the room as well as a “pile of assault weapons and a knife in one corner”.
Files in Yang’s room indicated that he was from Shandong Province, according to the Standard, which reported that postcards on the wall suggest he had been living in the apartment since 2016. A large drone was also found in his room.
His roommate, who refused to be identified, said Yang had been acting “oddly in recent months”.
She added: “If he became radicalised, it was recent.”
What has the Chinese consulate said?
The Chinese diplomatic post in San Francisco issued a statement about the incident, saying an “unidentified person drove violently into the document hall of the consulate, posing a serious threat to the safety of the staff and people at the scene, and causing serious damage to the facilities and property of the consulate”.
The consulate added that it “strongly condemns this violent attack and reserves the right to pursue responsibility for the incident”.
“Our mission has made solemn representations to the United States, demanding that the truth be quickly ascertained and dealt with seriously in accordance with the law,” the statement continued.
The US state department, meanwhile, has not yet responded to the incident.
The Consulate General of the People’s Republic of China is on a major street near the California city’s Japantown neighbourhood.
The incident took place a month before Chinese president Xi Jinping is expected to attend the Asia-Pacific Economic Cooperation Leaders Meeting in the city.
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