The gunman who held 17 people hostage inside a Sydney, Australia, café for 16 hours should never have been out on bail, his murdered ex-wife's family said on Tuesday.

Noleen Hayson Pal, 30, had sought refuge in the San Francisco Bay Area before being murdered by her abusive ex-husband in April 2013, her relatives told CBS San Francisco station KPIX-TV.

On Tuesday, a terrifying 16-hour siege came to an end after a swarm of heavily armed police officers stormed inside the Lindt Chocolat Café, killing gunman Man Haron Monis, a self-proclaimed Islamic "sheikh" from Iran who had migrated to Australia in 1996.

But the entire incident could have been avoided if the 49-year-old gunman had been jailed over Pal's murder, Ayyut Khalik, Pal's godfather, told KPIX. Despite facing charges of being an accessory to the murder of his ex-wife, Monis had been let out on bail.

"He was a scam artist, oh yeah. A liar, a scam artist," Khalik said. "He should have been hanged a long time ago. But you're innocent until proven guilty."

Although he didn't trust Monis, Khalik never believed that the 49-year-old would be capable of carrying out a terrorist attack. "I never thought he would do something like that, no," he said.

In 2003, Khalik was introduced to Monis after his goddaughter got married to him, New York Daily News reported. Over a year ago, Pal came to stay with him in the U.S. after Monis allegedly became extremely abusive toward her after the birth of their two children.

"He was abusing her, having her wear the hijab, did not want her to talk with anybody," Khalik said, adding that Pal returned to Australia a month later because of the children.

Six months later, Monis allegedly stabbed Pal 18 times before setting her on fire. While Monis' girlfriend, Amirah Droudis, was accused of his ex-wife's murder, he was only charged with being an accessory and was bailed out of jail two weeks later.

"Two weeks later, he was out on bail. And you know, if he would have still been in jail, this would not have happened," Khalik added.

However, Monis had reportedly also been arrested earlier this year on charges of sexually assaulting a 27-year-old woman in 2002. Despite the red flags, he was never on any kind of terror watch list, Prime Minister Tony Abbot said Tuesday.

"If I can be candid with you, the question we (are) asking (is), 'How can someone who has had such a long and checkered history not be on the appropriate watch lists, and how can someone like that be entirely at large in the community?'," Abbott said at a press conference, describing the gunman as "deluded and sick."

"We are all outraged that this guy was on the street," New South Wales Premier Mike Baird said. "We need to ensure that everything is done to learn from this."

Meanwhile, Tuesday's siege resulted in the death of two hostages - 38-year-old barrister and mother of three, Katrina Dawson, and 34-year-old Lindt Cafe manager, Tori Johnson.