Sydney (CNN) -- Australian special forces troops and police stormed the cafe where a self-styled Muslim cleric had been holding hostages early Tuesday, killing the gunman and ending a crisis that had paralyzed central Sydney for hours.

A national security source in the United States said the combined military-police team entered the Lindt Chocolate Cafe from two directions early Tuesday morning and killed the man, identified by an official with direct knowledge of the situation as Man Haron Monis.

Police didn't say if anyone else was hurt in the raid, but video shot by Australian media showed people being taken from the scene on stretchers, and Australian media reported some people may have been killed and others wounded.

Police declined to comment to CNN but said on Twitter that details of the incident were to come.

The raid ended the 16-hour standoff but left many other questions unanswered: What did the gunman want? Why did he choose the cafe as his target? And was he acting alone?

Man Haron Monis.

Before the raid, Monis had demanded a flag and phone call with Prime Minister Tony Abbott, CNN affiliate Sky News Australia reported. He made the demands through hostages who contacted media organizations, Sky News reported.

Some hostages had also reportedly posted messages to social networking sites and the YouTube online video service. Police urged media early Tuesday not to show the videos.

Monis, also known as Sheikh Haron, pleaded guilty in 2013 to writing letters to relatives of Australian service members saying they were "Hitler's soldiers," according to Australian media reports.

He was believed to be acting alone, and he didn't appear to be part of a broader plot, additional U.S. law enforcement and intelligence sources said Monday.

Grenades, gunfire as heavily armed police storm Sydney cafe

How the siege unfolded

Hundreds of police officers, including snipers, surrounded the cafe in Sydney's central business district shortly after the gunman took over the building at 10 a.m. Monday (6 p.m. ET Sunday).

 

<cite class="expCaption">Police: Hostage safety is our top priority</cite>

 

<cite class="expCaption">Australian Police: We have had contact </cite>

<cite class="expCaption">MAP: Sydney central business district</cite>

<cite class="expCaption" id="cite413">Photos: Hostage situation in Sydney</cite>

Chilling images from Australian media on Monday showed people, believed to be hostages, with their hands pressed against the cafe's windows. They were holding up a black flag with Arabic writing on it reading, "There is no God but God and Mohammed is the prophet of God."

Five hostages sprinted out of the cafe toward heavily armed police officers several hours into the standoff, sending the gunman into an agitated tirade, according to an Australian reporter.

Chris Reason, a correspondent for CNN affiliate Seven Network, said the gunman became "extremely agitated" when he realized what had happened and "started screaming orders" at the remaining hostages.

Reason said he could see the gunman pacing past the cafe's windows from his vantage point at the network's nearby offices. He described the man as unshaven, wearing a white shirt and black cap and carrying a shotgun.

As night fell, lights went out in the cafe, Reason reported.

After a tense night, police could be seen early Tuesday throwing flash-bang grenades into the cafe in video aired by Seven Network.

Gunfire erupted amid the chaos. After a brief episode of violence, the crisis appeared to ease, with police officers assuming a more relaxed pose, according to Australian media.

Video captured medics working on some people and others being carried away in stretchers.

Tiffiny Genders, a police reporter for 2GB radio, told CNN the freed hostages had been taken to hospitals under police guard.

Australians worried

The hostage situation left Australians shaken.

Australian Prime Minister Tony Abbott called it "profoundly shocking" in a series of Tweets.

"It's been a difficult day, which has tested us, but like Australians in all sorts of situations, we have risen to the challenge," he said.

CNN's Anna Coren reported from Sydney, Michael Pearson reported and wrote from Atlanta, and Jethro Mullen reported and wrote from Hong Kong. CNN's Dana Ford, Hilary Whiteman, Euan McKirdy, Chieu Luu, Elizabeth Joseph and Khushbu Shah also contributed to this report.