A Mississauga man is sounding the alarm about a brazen theft at a fast food restaurant that cost him his laptop and crucial personal documents.

Balaji Devatha Venkatesh even got to see it happen after the fact, thanks to security camera video from the scene.

"It was the biggest shock of my life because it never happened to me and also the fact that unfortunately I had all the important documents in my backpack," Venkatesh told CBC News.

It all started when he went into the Chick-fil-A near the intersection of Yonge and Bloor Streets last Friday. He was there between 9:15 p.m. and 9:45 p.m.

Security footage shows Venkatesh sitting at a countertop and eating with a friend, with his backpack on the floor. A man in jeans and a black coat can also be seen circling around the table, and at times on his phone.

The man then uses his feet to pull and kick Venkatesh's backpack away from him. Video shows the man then picking it up and simply walking out the door.

WATCH: Venkatesh's backpack is stolen

Security camera video of a man stealing a backpack inside a Toronto Chick-Fil-A. 1:18

"The seats were a bit high ... and then I was not concentrating what was happening to my bag because it was out of my view," Venkatesh said. "As soon as we finished our dinner we thought okay let's get going ... and then I see my backpack is not there anymore."

Venkatesh contacted the restaurant, and that's where the owner provided him with a copy of the video showing what happened.

The impact of the theft is worsened because he had important documents in his backpack, alongside his laptop.

"I lost my passports, both Indian passport and Canadian passport, and I lost my citizenship certificate," he said. He also lost his landing papers.

Const. Sidhu says belongings should never be left unattended (Wasim Zaitoun/CBC)

The mechanical engineer reported what happened the next day to Toronto police.

"It's currently an open investigation. Hopefully the property is retrieved," Const. Jeniffer Sidhu told CBC Toronto.

"Thefts of personal property such as knapsacks, [and] purses happen on a daily basis. However it's not always reported to police," she said.

Sidhu stressed that any thefts of important documentation like passports must be reported to police.

Venkatesh said it will take about seven months to get all those documents back.

He also had a message for the man who grabbed his bag.

"If I get my documents back I'm good," he said. "He can keep the laptop."

Sidhu said people should make sure to watch their bags at all times.

"So if you have your backpack or your purse at the back of your chair, all they need to do is slowly walk over, take off one handle over some time, walk over and grab the other handle and off they go with your knapsack," she said.