ELLIOT LAKE, Ont. -- The inquiry into why a northern Ontario mall collapsed last summer killing two women and injuring dozens of others enters its final phase Monday, with the first of two key witnesses taking the stand.

Slated to testify over the next two weeks about their roles in the tragedy are Levon Nazarian and his father Bob Nazarian, who owned the ill-fated Algo Centre Mall for its final seven years.

"The evidence that we've heard so far is that conditions continued to deteriorate over that period," said inquiry lawyer Peter Doody.

"We expect these two will give us evidence about what they did to deal with the situation and explain what was happening."

Much of the community's anger over the tragedy -- the result of decades of water and salt penetration that rotted the steel supporting the roof-top garage -- has been directed at the Nazarians.

Levon Nazarian, 29, who worked for Eastwood Mall Inc., as an independent contractor and an administrator, is slated to testify first.

Witnesses have described Bob Nazarian, who turns 68 next week, as someone who could be charming, but also as a tight-fisted bully who fired employees and contractors at will and badgered others into falsifying documents to downplay the mall's state of disrepair.

Evidence before the inquiry to date is that Nazarian either would not or could not do what was needed to save the mall, whose problems began with its poor design and construction in 1979.

"It is very concerning ... when lives are at stake and Mr. Nazarian has blatant disregard to provide adequate safety measures in his hotel and mall," former mall manager Henri McCleery said in one statement.

"Mr. Nazarian has always tried to take short cuts."

Nazarian, of Richmond Hill, Ont., bought the mall through his company, Eastwood Mall Inc., from its second owner in 2005. He has said he spent about $1 million on repairing a roof beset with problems he inherited unwittingly.

"A lot was hidden from Bob before he bought the mall," John Beaudin, a mall maintenance worker, told police last year. "They made it look good."

In an interview with The Canadian Press earlier this year, Nazarian denied doing anything illegal. He accused the media of "twisting these things and making them negative."

Nazarian's lawyer, Michael Title, has said a series of engineering reports done after 2004 -- including one done for the Royal Bank ahead of advancing a $3-million mortgage -- rang no alarm bells.

"All of the reports that I've read would have convinced me that everything was fine," Title said in an interview in March. "The structure was deemed structurally sound as late as May 2012."

The inquiry has since heard Nazarian pressed an engineer to alter an inspection report to downplay the problems in the weeks before the collapse.

Commission counsel has met with the Nazarians, but Doody would not elaborate.

Doody did say a long-running battle over access to Nazarians' documents that required intervention from an arbitrator has now been resolved.

On June 23, 2012, part of the roof-top parking deck caved in on staff and shoppers, sparking a frantic but fruitless search of the rubble for survivors. Days later, searchers pulled the bodies of Lucie Aylwin, 37, and Doloris Perizzolo, 74, from the twisted remains.

The Nazarians will be among the last of about 70 witnesses testifying at Part 1 of the inquiry into the causes of the collapse.

Part 2, which will look at the emergency response to the collapse, is slated to begin at the end of the month.