Last weekend, the stylish new Piazza at Schmidts complex in Northern Liberties became the scene of a shocking and grisly double murder.

Thanks to cameras installed throughout the complex, police have seen much of the crime with their own eyes. Much of the footage was too graphic to share with the public, police said.

Law enforcement officials are investigating the meticulously calculated double homicide, which occurred at about 5:30 p.m. Saturday night in The Navona - a luxury apartment complex connected to the bustling Piazza at Schmidts complex in Northern Liberties.

Surveillance footage taken by cameras in the building was released on Monday by police, and shows the victims, 34-year-old party promoter, Rian Thal, and 40-year-old Timothy Gilmore, a firefighter from Winchester, Ohio, being gunned down in a hallway on the seventh floor of the building. The pair walked into a fatal trap set by the four men suspected in the murder.

Police are still reviewing surveillance footage, but what they have released shows just how the three gunmen - along with another individual acting as a lookout - carried out the brazen midafternoon shooting.

During a press conference held earlier this week, Capt. James Clark of the Philadelphia Police's Homicide Unit, narrated silent footage of the crime, illustrating how the men obtained access to the building and how they prepared for the crime by waiting for their victims for almost a half-hour.

As shown on a time-stamped tape, one person, a black man who Clark described as the first shooter, arrived at the building around 5 p.m.

The man, who wore a white T-shirt, jeans and a baseball hat, got in the building by simply catching the lobby door after someone else walked inside.

Talking on a cell phone the entire time, that man was seen on video heading to the second floor of the building and looking around the area. He then returned to the lobby, still on his phone, and he sat down and waited.

After a period of time, that man opened the lobby door, allowing two other men, who police identified as the additional shooters, to enter the building.

The two new arrivals - a heavy-set black man wearing a long white T-shirt that hung down to his knees and blue jean shorts and a dark baseball cap, and a taller, thinner black man who wore and orange shirt, white ball cap and jeans - joined the first man. They all were caught on tape as they proceeded to climb the stairs to the sixth floor.

Another man, who Clark said was probably a lookout and might have been "orchestrating" the crime, is also shown on tape.

However, Clark said that police have "no idea" how the fourth suspect, a black man in a white T-shirt and lightly colored shorts, entered the building.

He was shown on tape talking on his phone while walking along the sixth-floor after the other men had moved to the floor above.

The video showed two of the gunmen as they took positions in stairwells on the seventh floor, where Thal's apartment was located, to prepare for the ambush.

Another shooter took a position near Thal's apartment door while the man acting as lookout stayed on the sixth floor and yelled up through the stairwells while he searched out of windows on the floor below.

Clark said that this man was watching the street to notify the shooters of the victims' arrival.

When Thal and Gilmore finally appear in the video, the gunmen are in hiding.