One of the hostages who was held at a Lindt chocolate café in Sydney, Australia managed to covertly send a text message to his mother during the ordeal, telling her he's "OK" and that he "can't talk."

A Sydney woman says her son was among the hostages held at a chocolate café in heart of the city, where police recently ended a tense 16-hour standoff. Police stormed the building early Tuesday morning and freed the hostages. The gunman and two hostages – a 34-year-old man and 38-year-old woman -- were killed in the ordeal.

The mother told Sydney's 2GB radio that her son is an apprentice plumber who probably stopped at the café to get coffee in the morning, and became embroiled in the hostage situation.

The mother, who goes by the name Mel, says she received a text message from her son about five hours into the crisis, telling her he was inside.

"Mum, I'm in the Lindt café in Sydney," the message said.

"My heart just dropped," Mel told 2GB radio. "I sent him a text saying, 'What's going on, are you OK?'" she told the radio station.

Her son's reply was brief: "I'm OK mum, can't talk."

The hostage situation started at about 9:45 a.m. local time in Sydney, and ended early Tuesday morning.