It appears to be a kind gesture, holding a door open for someone you think is likely your neighbor.
But that gesture backfired for a 78-year old Koreatown woman on Friday.
A young woman followed the older woman into her Berendo Street apartment and snatched her purse.
The older woman struggles for the bag until the suspect pushes her to the ground, running off with it.
The elderly lady quickly gets up, even following after the suspect, but never catches up.
"This was absolutely a crime of opportunity," says LAPD Sgt. Hamed Mohammadi.
Even LAPD detectives who see so much, were rattled.
"It hit me pretty hard, I was picturing my mom getting injured and I wanted the media, I wanted the citizens of Los Angeles to view this video to make sure we apprehend the suspect," says LAPD Detective Daniel Chi.
Police describe the suspect as a black woman about 5 feet 8 inches, 140 pounds in her early 20s with red hair.
Police hope someone recognizes her from the video.
As for the victim, LAPD detectives say she was shaking as they were talking to her, but she did not need to go to the hospital and is expected to be OK.