MIAMI -- A surveillance video released Friday shows Rigoberto Alpizar at the airport in Quito, Ecuador, just hours before he was shot by air marshals after threatening to have a bomb on American Airlines Flight 924 Wednesday.

The tape clearly shows Alpizar acting unstable and aggressive at the airport in Quito, NBC 6's Tom Llamas reported.

In the video, Alpizar grabbed another passenger on two occasions, his wife trying to stop him.

"She told us her husband was diagnosed as being bipolar approximately 10 to 12 years ago. He hadn't been taking his medication," Miami-Dade Police Chief Willie Marshall said Thursday.

The video tape shows Alpizar arguing with the ticketing agent before boarding. The argument was apparently not serious, because Alpizar boarded the flight.

Several hours later and allegedly without his medicine, he boarded Flight 924 at Miami International Airport. According to passengers, he started acting erratically.

"There was some kind of mayhem happening, and then all of a sudden, this man ran through the cabin, and she ran after him, and people were like, 'What's going on?' passenger Mary Gardner said.

Investigators said he was wearing his backpack on the front, just as he is in the surveillance video, when he told the air marshals on the plane that he had a bomb.

No weapons or bombs were found on Alpizar or on the plane.