The video of the incident shows a white officer detaining Johnson.
During an afternoon news conference Wednesday, La Mesa police Chief Walt Vasquez said the officer initiated the contact after suspecting Johnson was smoking in the transit station area, which is prohibited.
A six-minute video captured by a friend of Johnson's was shared on social media, bringing attention to the case and prompting in part a large protest in La Mesa on Saturday.
La Mesa city and police officials on Wednesday released police body camera video of a controversial arrest last week of a 23-year-old black man at a trolley station, an incident that spurred calls for police reform and social justice.
The La Mesa encounter happened two days after video emerged of Minnesota police officer with his knee on the next of a handcuffed black man for several minutes, even as the man, George Floyd, pleaded that he could not breathe.