SAN FRANCISCO (KGO) -- Police are investigating after a stabbing occurred in front of a San Francisco elementary school after a crash Tuesday morning, as children were being dropped off.It happened around 8:30 a.m., outside Sheridan Elementary School in the Ingleside District.Police told ABC7 News two cars were involved in a minor crash. The woman in the car who was hit told police the other driver, a babysitter dropping a child off, didn't yield.Lizzette Hasbon said the babysitter got out of the car and approached her very aggressively, so she felt threatened, and grabbed a scalpel she keeps with her. "She just started cursing and yelling, and literally had me behind my car, and my child was in there. I was like, 'I will defend myself if you don't back up,'" Lizzette Hasbon said. "She didn't listen so I had to defend myself with a little knife."Both women were still on the scene when officers arrived, and the injured woman was taken to a hospital with injuries not considered life-threatening.San Francisco Ofc. Giselle Talkoff said Hasbon was released after investigators determined that the stabbing appeared to have been a case of self-defense, Talkoff said.Police confiscated Hasbon's scalpel.While the incident occurred near Sheridan Elementary School, it did not involve the school in any way, Talkoff said.