If this is the incident you're referring to, then:

Updated Wednesday June 14 2:10 p.m. EST - San Francisco Police have provided this statement to Jalopnik:

“The SFPD is aware of the social media video showing an autonomous vehicle stopped in the middle of a road during a recent shooting incident in San Francisco. The autonomous vehicle did not delay police, fire, or other emergency personnel with our arrival or departure from this scene. Furthermore, it did not interfere with our investigation into the shooting incident.

Also, if the lives saved by autonomous cars are anywhere near as high as they're supposed to be, isolated incidents are way more than worth it. Statements like "The very first time one of these things blocked emergency services, the whole project should have been shelved" are incredibly shortsighted and would result in orders of magnitude more deaths over time.