VANCOUVER -- The 15th-floor condo unit where half a dozen people, including two innocent bystanders, were gunned down in a gangland execution near Vancouver six years ago was frequented by a revolving cast of shady characters who the building's managers believed were buying and selling drugs, the trial for three people accused in the mass killing heard Tuesday.

Building manager Tracy Carothers said she was so concerned about unit 1505 of the Balmoral Tower, located in Surrey, that when fireplace repairman Ed Schellenberg and his nephew Zach were servicing the building on Oct. 19, 2007, Carothers suggested Schellenberg handle the unit because of the sort of people inside.

"I had mentioned to Ed that I didn't think it would be a good environment for Zach to go into, because young men of questionable behaviour (were inside)," Carothers testified at the trial of three alleged gang members facing murder and conspiracy charges.

"I just felt Zach was young and (it was) not a good environment for him."

On that Friday afternoon six years ago, Carothers was accompanying Schellenberg as he entered units on the 15th floor to service the building's gas fireplaces.

Before her conversation with Schellenberg, Carothers knocked on the door of unit 1505, where she was greeted by two Asian men she had never met before and the unit's tenant, who she knew as Chris Baldini. She also encountered a fourth man in the hallway, described as a young Asian man, who later walked into the unit, she said.

Carothers left Schellenberg behind on the 15th floor as he walked into unit 1505 to begin his work. It was the last time she saw him.

Schellenberg and Chris Mohan, a 22-year-old student who lived across the hall, were shot along with four other men who had ties to gangs and drugs. The Crown has alleged the killing began as a hit on a drug rival, but five more, including Schellenberg and Mohan, were killed to eliminate potential witnesses.

The other victims were Corey Lal, who the Crown contends was the intended target of the shooting, Lal's brother Michael, Edward Narong and Ryan Bartolomeo.

Matthew Johnston, Cory Haevischer and Quang Vinh Thang (Michael) Le are now on trial for various murder and conspiracy charges. A co-accused has already pleaded guilty and another, alleged gang leader Jamie Bacon, is scheduled for trial next year.

Johnston and Haevischer are accused of being directly involved in the killing, along with another man who cannot be named, while Le and Bacon -- who the Crown alleges were the leaders of the Red Scorpions gang -- are accused of being part of the conspiracy.

The trial has heard the apartment where the shooting took place, which the Crown has described as a "stash house," had a history of tenants suspected of being involved in the drug trade. The unit was owned by a man who also owned several other condos in the development, renting them out to tenants.

Carothers' husband, Norman Carothers, told the trial an earlier tenant also rented an apartment in a series of nearby low-rise buildings known as Balmoral Court. Norman Carothers said he "busted" that tenant for keeping a grow-op in his Balmoral Court apartment, and within a few weeks, that tenant moved out.

After that, a tenant named Raphael Baldini rented unit 1505 with his girlfriend, the court heard, and eventually the unit changed hands again, this time to Chris Baldini, identified as Raphael's cousin.

Raphael Baldini was a tall, skinny man in his 20s who appeared to be Italian, said Tracy Carothers. Chris Baldini was a short man in his late 20s with a Mediterranean complexion, she said. They did not appear to be related, she said.

All the while, unit 1505 had frequent visitors at all hours of the day, often staying for just a few minutes, some of them driving away in expensive cars, Tracy and Norman Carothers told the court.

"The number of people coming and going frequently -- we have experience seeing other drug transactions on the property," said Tracy Carothers.

"It became familiar to us."

The condo development, where Tracy and Norman Carothers worked until this past June, is located half a block from a station along the region's SkyTrain light-rail transit system in an area of Surrey with a reputation for drugs and crime, the court heard.

The security cameras in the parkade, where the Crown alleges the killers entered the building, had been stolen and had not been replaced by Oct. 19, 2007. Cars parked in the non-secure visitors area of the parkade were regularly broken into or vandalized. Even the protective padding used to cover the walls of the freight elevator when tenants moved in and out had been stolen.

As it turns out, another person in the building also had a connection to the Red Scorpions gang and forms a key piece of the Crown's theory about what happened the day of the shooting. The Crown alleges another tenant gave Johnston the key fob that Johnston, Haevischer and the third man used to enter the building before the murders.

The name of the tenant who allegedly provided the fob is covered by a publication ban.

Some of the testimony on Tuesday focused on security access records that indicate the times and locations each of the building's fobs were used to enter the Balmoral.

A fob belonging to a tenant who lived on another floor was used to gain access to the building at 2:23 p.m. on Oct. 19, the trial heard, which is the about the same time the Crown alleges the trio of attackers entered the Balmoral.

That was the last time the fob was used.

Johnston, Haevischer and Le watched the proceedings from the prisoners' box behind nearly a dozen defence and Crown lawyers.

Johnston and Haevischer, both with large muscular builds and short-cropped hair, each wore dress shirts with dark vests. During one break, both of them smiled and gestured to someone in the public gallery.

Le, who wore a grey sweater over a white shirt, regularly took notes on a pad of paper.

Two layers of thick Plexiglas protected them from the gallery, where dozens of people observed the trial under heavy security.

Johnston and Haevischer each face six counts of first-degree murder and one count of conspiracy.

Le is charged with one count of first-degree murder and one count of conspiracy.

The three men have all pleaded not guilty.

Jamie Bacon is scheduled to stand trial separately next year on charges of first-degree murder and conspiracy.