It comes as San Francisco police announce they are now investigating the incident.
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Kit Lam says he was collecting signatures on May 30 when a man, San Francisco police are not naming, offered to sign the petition but then took the clipboard with other people's signatures and addresses.
A witness shared video she shot near 3rd Avenue and Clement Street with ABC7 News.
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"You took the petitions I saw you," shouted Lam in the video.
"I was shocked and angry at the same time," Lam told ABC7 News.
Lam and the witness followed the man.
"I looked at it, I decided I didn't want it anymore I don't have your (expletive)," said the man in the video.
"I couldn't believe it because I saw him toss the clipboard under the car," said Lam.
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Another person spotted the clipboard underneath a car.
"There you got it back. I'm sorry. You caught me. You caught me," said the man in the video.
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"And I realized some petitions are still missing," Lam told ABC7 News.
"Where is the other ones? Where is the other ones," Lam asks in the video.
The man took the other signatures out of the back of his jeans and gave them to Lam.
"I was just furious and why would someone do this, why?" said Lam.
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"Stop you are breaking the law," Lam says in the video.
"There's a misconception that immigrants, Asian immigrants do not speak up and I think he's wrong," said Lam.
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Lam reported the incident to SFPD.
"Our investigators who are diligently working on the case are gathering information and have leads that they're following up on," said Officer Robert Rueca.
The man emptied his pockets saying he didn't have anymore.
"What is your name sir? What is your name? Why are you doing this," Lam says in the video.
Lam says he hopes SFPD makes an arrest.
SFPD says because petition signatures for a ballot measure are involved, it is possible they will coordinate with other law enforcement agencies.