A man sitting in his Jeep pulled a knife on the suspect who punched him and stole his SUV in Grant Hill, according to San Diego police.
Thursday evening, the victim was in his Jeep Cherokee in the 2500 block of L Street when a man walked up to him and started hitting him in the face, police say.
As the victim was hit over and over, he reached for a pocket knife and stabbed the suspect at least once.
The punches stopped, but the suspect was able to pull the victim out of his vehicle and escape in it.
Using lojack tracking technology, the SDPD tracked the suspect to Spring Valley, pulled him over and arrested him.
Both men are being taken to the hospital for their injuries.
The incident is under investigation.